OSD::RemoveWQ: do not apply_transaction while blocking _try_resurrect_pg

Some callbacks take the osd lock, so we need to avoid blocking an
osd lock holding thread while waiting on a filestore callback.
Instead, just queue the transaction, and allow _try_resurrect_pg
to cancel us while we are waiting for the transaction to go through
(CLEARING_WAITING).

Signed-off-by: Samuel Just <sam.just@inktank.com>