crimson/osd: check if req should be server with obc lock

crimson/osd: check if req should be server with obc lock

there is chance that osdmap is updated after the obc lock is acquired
for a certain object, and before the lock is acquired, the OSD is able
to serve the request. and the updated osdmap changes the OSD from
primary to a stray OSD of the PG in question. so we need to move the
check closer to where we actually handle the op.

Fixes: https://tracker.ceph.com/issues/47212
Signed-off-by: Kefu Chai <kchai@redhat.com>