In rare cases a scheduled transaction is not scheduled correctly and we need
to remove it from the tx-queue in order to re-schedule. When we pull it from tx-queue
and it has been located at the head, we must poll-execute the next txs in the queue.
1. Fix the bug.
2. Improve verbosity loggings to make it easier to follow up on tx flow in release mode.
3. Introduce /txz handler that shows currently pending transactions in the queue.
4. Fix a typo in xdel() function.
5. Add a py-script that reproduces the bug.
Signed-off-by: Roman Gershman <roman@dragonflydb.io>
