provider/docker: added support for linux capabilities (#12045)

* added support for linux capabilities

Refs #11623

Added capabilities block
Added tests for it
Added documentation for it.

My PC doesnt support memory swap so it errors there.

```
$ make testacc TEST=./builtin/providers/docker TESTARGS='-run=TestAccDockerContainer_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/02/17 14:57:08 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/docker -v -run=TestAccDockerContainer_ -timeout 120m
=== RUN   TestAccDockerContainer_basic
--- PASS: TestAccDockerContainer_basic (44.50s)
=== RUN   TestAccDockerContainer_volume
--- PASS: TestAccDockerContainer_volume (40.73s)
=== RUN   TestAccDockerContainer_customized
--- FAIL: TestAccDockerContainer_customized (50.27s)
	testing.go:265: Step 0 error: Check failed: Check 2/2 error: Container has wrong memory swap setting: -1
	Please check that you machine supports memory swap (you can do that by running 'docker info' command).
=== RUN   TestAccDockerContainer_upload
--- PASS: TestAccDockerContainer_upload (38.56s)
FAIL
exit status 1
FAIL	github.com/hashicorp/terraform/builtin/providers/docker	174.070s
Makefile:48: recipe for target 'testacc' failed
make: *** [testacc] Error 1
```

* Documentation changes.

* added maxitems and rerun tests

resource_docker_container.go

@@ -138,6 +138,33 @@ func resourceDockerContainer() *schema.Resource {
 				ForceNew: true,
 			},
 
+			"capabilities": &schema.Schema{
+				Type:     schema.TypeSet,
+				Optional: true,
+				ForceNew: true,
+				MaxItems: 1,
+				Elem: &schema.Resource{
+					Schema: map[string]*schema.Schema{
+						"add": &schema.Schema{
+							Type:     schema.TypeSet,
+							Optional: true,
+							ForceNew: true,
+							Elem:     &schema.Schema{Type: schema.TypeString},
+							Set:      schema.HashString,
+						},
+
+						"drop": &schema.Schema{
+							Type:     schema.TypeSet,
+							Optional: true,
+							ForceNew: true,
+							Elem:     &schema.Schema{Type: schema.TypeString},
+							Set:      schema.HashString,
+						},
+					},
+				},
+				Set: resourceDockerCapabilitiesHash,
+			},
+
 			"volumes": &schema.Schema{
 				Type:     schema.TypeSet,
 				Optional: true,
@@ -396,6 +423,21 @@ func resourceDockerContainer() *schema.Resource {
 	}
 }
 
+func resourceDockerCapabilitiesHash(v interface{}) int {
+	var buf bytes.Buffer
+	m := v.(map[string]interface{})
+
+	if v, ok := m["add"]; ok {
+		buf.WriteString(fmt.Sprintf("%v-", v))
+	}
+
+	if v, ok := m["remove"]; ok {
+		buf.WriteString(fmt.Sprintf("%v-", v))
+	}
+
+	return hashcode.String(buf.String())
+}
+
 func resourceDockerPortsHash(v interface{}) int {
 	var buf bytes.Buffer
 	m := v.(map[string]interface{})

resource_docker_container_funcs.go

@@ -126,6 +126,15 @@ func resourceDockerContainerCreate(d *schema.ResourceData, meta interface{}) err
 		hostConfig.VolumesFrom = volumesFrom
 	}
 
+	if v, ok := d.GetOk("capabilities"); ok {
+		for _, capInt := range v.(*schema.Set).List() {
+			capa := capInt.(map[string]interface{})
+			hostConfig.CapAdd = stringSetToStringSlice(capa["add"].(*schema.Set))
+			hostConfig.CapDrop = stringSetToStringSlice(capa["drop"].(*schema.Set))
+			break
+		}
+	}
+
 	if v, ok := d.GetOk("dns"); ok {
 		hostConfig.DNS = stringSetToStringSlice(v.(*schema.Set))
 	}

resource_docker_container_test.go

@@ -128,6 +128,22 @@ func TestAccDockerContainer_customized(t *testing.T) {
 			return fmt.Errorf("Container has wrong dns search setting: %v", c.HostConfig.DNS[0])
 		}
 
+		if len(c.HostConfig.CapAdd) != 1 {
+			return fmt.Errorf("Container does not have the correct number of Capabilities in ADD: %d", len(c.HostConfig.CapAdd))
+		}
+
+		if c.HostConfig.CapAdd[0] != "ALL" {
+			return fmt.Errorf("Container has wrong CapAdd setting: %v", c.HostConfig.CapAdd[0])
+		}
+
+		if len(c.HostConfig.CapDrop) != 1 {
+			return fmt.Errorf("Container does not have the correct number of Capabilities in Drop: %d", len(c.HostConfig.CapDrop))
+		}
+
+		if c.HostConfig.CapDrop[0] != "SYS_ADMIN" {
+			return fmt.Errorf("Container has wrong CapDrop setting: %v", c.HostConfig.CapDrop[0])
+		}
+
 		if c.HostConfig.CPUShares != 32 {
 			return fmt.Errorf("Container has wrong cpu shares setting: %d", c.HostConfig.CPUShares)
 		}
@@ -311,6 +327,12 @@ resource "docker_container" "foo" {
 	memory = 512
 	memory_swap = 2048
 	cpu_shares = 32
+
+	capabilities {
+		add= ["ALL"]
+		drop = ["SYS_ADMIN"]
+	}
+
 	dns = ["8.8.8.8"]
 	dns_opts = ["rotate"]
 	dns_search = ["example.com"]