osd: don't spew spurious scrub unreserve messages

osd: don't spew spurious scrub unreserve messages

The past primary was sending out scrub unreserve messages to all the
non-primary OSDs in the acting set on a PG state change. They're
spurious since the other OSDs will cancel the scrubs themselves
on state change, and they weren't right anyway because the loop
was looking at all the non-primary OSDs and sending out a message,
which could have excluded the new primary (if it was a replica before)
included other OSDs new to the PG, and included the current OSD.

Signed-off-by: Samuel Just <samuel.just@dreamhost.com>
Signed-off-by: Greg Farnum <gregory.farnum@dreamhost.com>