hook: add a generic hook after transaction has been closed
We are adding generic hooking for all transactions. We may have useful
information about what happened during the transaction, user of the transaction
should have filled the 'hookargs' dictionnary of the transaction. This hook is
simple because it has no power to rollback the transaction.
Testing that hghave does not crash when checking features
$ "$TESTDIR/hghave" --test-features 2>/dev/null