In case of DB outages when a flow is running, an exception is caught and
the flow is reverted. In most of the flows, the revert function of the
first task's (the last to be reverted) unlocks the load balancer by
setting its provisioning status (to ERROR or ACTIVE, depending on the
flow), but it fails if the DB is not reachable, leaving the LB in
a PENDING_* state.
This commit adds tenacity.retry to those functions, Octavia retries to
set the status during ~2h45 (2000 attempts, 1 sec initial delay, 5 sec
max delay).
Closes-Bug: #2036952
Change-Id: I458dd6d6f5383edc24116ea0fa27e3a593044146