## Problem
This test occasionally fails while the test teardown tries to do a
graceful shutdown, because the test has quickly written lots of data
into the pageserver.
Closes: #10654
## Summary of changes
- Call `post_checks` at the end of `test_isolation`, as we already do
for test_pg_regress -- this improves our detection of issues, and as a
nice side effect flushes the pageserver.
- Ignore pg_notify files when validating state at end of test, these are
not expected to be the same
a4d0a34591