osd/PG: do not assume delete event means found_missing

osd/PG: do not assume delete event means found_missing

This condition was introduced in 3a9d056d843bcafd26d78950b84e2844f8a3a9a1
as part of the missing deletes series, without a clear motivation.  The
best guess is that it was either compensating for some other unfound bug
or simply being a bit overaggressive.

The problem is that it triggers a notify being sent to the sender, or
restarts recovery, both of which are overreactions.

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 81d918d449f0211c8eac262e700930473f6e98a3)