[server] Add missing indices for undo support (closes #3259691)
The tables used by the 'undo' feature were missing some indices, which
among other things triggered repeated sequential scans when deleting old
transactions.
for table, column in [
('transactions', 'tx_time'),
('tx_entity_actions', 'tx_uuid'),
('tx_relation_actions', 'tx_uuid')]:
session.cnxset.source('system').create_index(session, table, column)
commit()