Make run/task/service :ID optional, default to zero/NULL

This patch makes the ':ID' field optional when registering non-inetd
run/taks/service etc.  It has always been optional in the .conf files,
but internally we defaulted to ':1'.

To open up for more useful conditions we now default to zero/NULL :ID,
meaning the user now *must* keep track of the :ID field if they have
multiple services with the same name.  This should already have been
an issue since such services would likely have conflicted with their
PID files (same name).  So it's unlikely to affect any user severely.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/service.c

@@ -977,20 +977,18 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 			parse_cmdline_args(svc, cmd);
 			goto inetd_setup;
 		}
-		if (!id) {
-			int n = svc_next_id_int(cmd);
 
-			if (n) {
-				snprintf(id_str, sizeof(id_str), "%d", n);
-				id = id_str;
-			}
+		/* inetd services need a unique ID, so we must always set one. */
+		if (!id) {
+			snprintf(id_str, sizeof(id_str), "%d", svc_next_id_int(cmd));
+			id = id_str;
 		}
 	}
 recreate:
 #endif
 
 	if (!id)
-		id = "1";
+		id = "";
 
 	svc = svc_find(cmd, id);
 	if (!svc) {