launch_daemon: Use BRoster::Launch() without registrar.

* BRoster now allows settings a "no-registrar" mode that is currently
  only honored in _LaunchApp(), though.
* Job::Launch() is now using this, which also allows launching
  applications by signature (ie. if the job name matches the
  signature, you can omit the "launch" option).

headers/private/app/RosterPrivate.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2007, Haiku.
+ * Copyright 2001-2015, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -52,6 +52,9 @@ class BRoster::Private {
 			{ return fRoster->_IsAppRegistered(ref, team, token, preRegistered,
 					info); }
 
+		void SetWithoutRegistrar(bool noRegistrar) const
+			{ fRoster->_SetWithoutRegistrar(noRegistrar); }
+
 		status_t RemoveApp(team_id team) const
 			{ return fRoster->_RemoveApp(team); }