commit: print "commit message saved in" message also if bookmark update fails
The bookmark update is done within the same transaction, so if fails,
the commit will also be rolled back.
I just happened to notice this while messing with this code; we have
not had reports of crashing bookmark updates from our users.
The same applies to the clearing of the merge state, although I don't
think that's currently tied into the transaction.
Differential Revision: https://phab.mercurial-scm.org/D5621