Remove the set `gp_fts_probe_retries to 1` which may cause FTS probe failed.
This was first added to reduce the test time, but set a lower retry
value may cause the test failed to probe FTS update segment
configuration. Since reduce the `gp_fts_replication_attempt_count` also
save the test time, so skip alter ``gp_fts_probe_retries`.

Also find an assertion may not match when mark mirror down happens before
walsender exit, which will free the replication status before walsender
exit and try to record disconnect info. Which lead the segment crash
and starts recover.