ctdb-client: Fix implementation of transaction start

ctdb-client: Fix implementation of transaction start

Since g_lock checks if the process exists in case of conflicting lock,
there is no need to register srvid.

Transaction start returns a transaction handle and transaction
commit/cancel will free that handle.  Since we cannot call async code
in a talloc destructor, this avoids the use of talloc destructor for
cancelling the transaction.

If user frees the transaction handle instead of calling transaction
cancel, it will leave stale g_lock lock.  This stale g_lock lock  will
get cleaned up on next transaction attempt.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>