Always include <errno.h> instead of <sys/errno.h>

Including <sys/errno.h> instead of <errno.h> raises a compiler warning
when building against musl libc.  Always include <errno.h> instead of
<sys/errno.h> to prevent that compilation warning from being triggered
and to achieve consistency in this regard across the entire source tree.

(cherry picked from commit b5cd146033)

bin/named/fuzz.c

@@ -19,7 +19,7 @@
 #ifdef ENABLE_AFL
 #include <named/globals.h>
 #include <named/server.h>
-#include <sys/errno.h>
+#include <errno.h>
 
 #include <isc/app.h>
 #include <isc/condition.h>

contrib/dlz/modules/common/dlz_dbi.c

@@ -41,6 +41,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
+#include <errno.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
@@ -48,8 +49,6 @@
 #include <stdlib.h>
 #include <ctype.h>
 
-#include <sys/errno.h>
-
 #include <dlz_minimal.h>
 #include <dlz_list.h>
 #include <dlz_dbi.h>

lib/isc/tests/errno_test.c

@@ -17,11 +17,10 @@
 #include <stddef.h>
 #include <setjmp.h>
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
-#include <sys/errno.h>
-
 #define UNIT_TESTING
 #include <cmocka.h>