tmpfiles: add --create and --remove flags

Allow execution of tmpfiles to specify which mode(s) of operation to run in.

plugins/bootmisc.c

@@ -162,7 +162,7 @@ static void setup(void *arg)
 	kernel_links();
 
 	/* Create all system tmpfiles.d(5) */
-	run_interactive(_PATH_TMPFILES, "Creating required directories and files");
+	run_interactive(_PATH_TMPFILES " --create", "Creating required directories and files");
 
 	/* Set BOOT_TIME UTMP entry */
 	utmp_set_boot();