Holding _session_lock for a whole write sequence buys certainty about what
the appliance saw and when, but blocks every poll and entity write for the
sequence's full length -- up to 10 x 30s. Which of those matters more
depends on what is being probed, so it is now hold_session_lock on
async_raw_write_sequence and a field on the service, defaulting to the
holding behavior that shipped.
Off, the lock is taken per write and released across the settle waits, so
entities keep updating through a long sequence. Exactly one of the two
context managers is ever the real lock -- asyncio.Lock isn't reentrant.
Tests assert the lock's actual state during the settle wait in both modes,
rather than just that the flag is accepted.
Marc Billow
6ee60beae9