fix procd service inactive

Exit directly will result procd service inactive and uci
configuration changes are no longer monitored.

Reported-by: Lvc Revincx <revincx233@gmail.com>
Signed-off-by: Tianling Shen <cnsztl@immortalwrt.org>

files/ua2f.init

@@ -68,7 +68,7 @@ start_service() {
 
 	local enabled
 	config_get_bool enabled "enabled" "enabled" "0"
-	[ "$enabled" -eq "1" ] || exit 1
+	[ "$enabled" -eq "1" ] || return 1
 
 	procd_open_instance "$NAME"
 	procd_set_param command "$PROG"