savecache: clean up creation of cache directory

The cache directory should be created via mkdir -p instead of
mkdir. This makes sure all parent directories are created.

Also, we now display an error message explaining that we were unable to
create the cache directory if creation fails.

init.d/savecache.in

@@ -25,12 +25,12 @@ start()
 	local rc=
 	if [ ! -d "$RC_LIBEXECDIR"/cache ]; then
 		rm -rf "$RC_LIBEXECDIR"/cache
-		if ! mkdir "$RC_LIBEXECDIR"/cache; then
+		if ! mkdir -p "$RC_LIBEXECDIR"/cache; then
 			rc=$?
 			if yesno "${RC_GOINGDOWN}"; then
 				rc=0
 			fi
-			eend $rc
+			eend $rc "Unable to create $RC_SVCDIR/cache"
 			return $rc
 		fi
 	fi