mkdir-label: don't use mkdirat_errno_wrapper() without reason

mkdirat_errno_wrapper(x,y,z) is identical to RET_NERRNO(mkdirat(x, y,
z)). Let's always use the latter when we can, because easier to read,
shorter.

The only reason to have mkdirat_errno_wrapper() at all is so that we can
pass a function pointer to it around. Otherwise, let's not use it.

src/shared/mkdir-label.c

@@ -2,6 +2,7 @@
 
 #include <sys/stat.h>
 
+#include "errno-util.h"
 #include "mkdir-label.h"
 #include "selinux-util.h"
 #include "smack-util.h"
@@ -16,7 +17,7 @@ int mkdirat_label(int dirfd, const char *path, mode_t mode) {
         if (r < 0)
                 return r;
 
-        r = mkdirat_errno_wrapper(dirfd, path, mode);
+        r = RET_NERRNO(mkdirat(dirfd, path, mode));
         mac_selinux_create_file_clear();
         if (r < 0)
                 return r;