tmpfiles: add --create and --remove flags to handle creation and removal tmpfile entries

The tmpfiles.d spec contains entry types that should be acted upon in different modes
of operation: create, clean, remove, and purge - so split finit logic operating on tmpfiles
entries into create and remove operations, which are already implemented.

Author: aanderse

plugins/bootmisc.c

@@ -162,7 +162,7 @@ static void setup(void *arg)
 	kernel_links();
 
 	/* Create all system tmpfiles.d(5) */
-	execl(_PATH_TMPFILES, _PATH_TMPFILES, NULL);
+	execl(_PATH_TMPFILES, _PATH_TMPFILES, "--create", NULL);
 
 	/* Set BOOT_TIME UTMP entry */
 	utmp_set_boot();