Allow calling signal-cli without -u flag

For daemon command all local users will be exposed as dbus objects
If only one local user exists, all other commands will use that user,
otherwise a user has to be specified.

src/main/java/org/asamk/signal/commands/UpdateGroupCommand.java

@@ -69,7 +69,7 @@ public class UpdateGroupCommand implements DbusCommand {
             return 1;
         } catch (DBusExecutionException e) {
             System.err.println("Failed to send message: " + e.getMessage());
-            return 1;
+            return 2;
         }
     }
 }