Transport master was not being taken because when the configuration variable is
set, AudioEngine::set_session() has not been called yet so
AudioEngine::reset_timebase() did nothing (the transport stuff at the beginning
of Session::when_engine_running() is questionable for the same reasons).
I am not sure if this is correct, but I have failed to more thoroughly figure
out the issue. At least Ardour actually sets Jack transport information now.
However, there are some discrepancies between Ardour time and Jack time, as
reported by Session::jack_timebase_callback().
Perhaps related, the transport master menu item does not restore correctly.
Previous to this commit, the only way to make a loaded session take transport
master was to "set" this out of sync item (which did nothing), then unset it,
then set it again, which would finally actually cause the configuration change.
git-svn-id: svn://localhost/ardour2/branches/3.0@12992 d708f5d6-7413-0410-9779-e7cbd77b26cf
39b42e3766