Adds fetching for MSSQL instance name

lib/mssql/Get-IcingaMSSQLInstanceName.psm1

@@ -0,0 +1,34 @@
+function Get-IcingaMSSQLInstanceName()
+{
+    param (
+        $SqlConnection              = $null,
+        [string]$Username,
+        [securestring]$Password,
+        [string]$Address            = "localhost",
+        [int]$Port                  = 1433,
+        [switch]$IntegratedSecurity = $FALSE,
+        [switch]$TestConnection     = $FALSE
+    );
+
+    [bool]$NewSqlConnection = $FALSE;
+
+    if ($null -eq $SqlConnection) {
+        $SqlConnection = Open-IcingaMSSQLConnection -Username $Username -Password $Password -Address $Address -IntegratedSecurity:$IntegratedSecurity -Port $Port -TestConnection:$TestConnection;
+
+        if ($null -eq $SqlConnection) {
+            return 'Unknown';
+        }
+
+        $NewSqlConnection = $TRUE;
+    }
+
+    $Query        = 'SELECT @@servicename'
+    $SqlCommand   = New-IcingaMSSQLCommand -SqlConnection $SqlConnection -SqlQuery $Query;
+    $InstanceName = (Send-IcingaMSSQLCommand -SqlCommand $SqlCommand).Column1;
+
+    if ($NewSqlConnection -eq $TRUE) {
+        Close-IcingaMSSQLConnection -SqlConnection $SqlConnection;
+    }
+
+    return $InstanceName;
+}