WatchAction::onSubmit return correct value, not always true

WatchAction::onSubmit return correct value, not always true

The onSubmit method documentation states, that the caller can expect either
true for a successfull run, false if not tried and an array of error messages
in case of an failure. WatchAction however always returned false, even though
a Status object is availble with all needed information.

The behaviour of WatchAction::onSubmit is now changed to return the appropriate
value taken from the returned Status object of WatchAction::doSelf.

Also:
 * Added WatchAction test class to higher test coverage, especially for the
   static methods
 * Marked getUnwatchToken as deprecated, it's not used and a caller can easily
   switch to getWatchToken with "unwatch" as the action parameter

Change-Id: I2c1b91e1884a0d5f27f5e7ab9eafd6173642c21c