PGLog: trim mod_desc after appending to the log

We'll want he callers up the chain to take the log
entry as a const ref.

Signed-off-by: Samuel Just <sjust@redhat.com>
PG::add_log_entry: no need to 0 offset in append_log

No longer used.

Signed-off-by: Samuel Just <sjust@redhat.com>
osd/: pass log_entries in write path as const ref

We need to use them after the submit_transaction call, so
we can't pass them by non-const ref.

Signed-off-by: Samuel Just <sjust@redhat.com>
osd/: s/backfill_read/recovery_read for obc locking

We are going to expand our usage of this for normal
replica recovery.

Signed-off-by: Samuel Just <sjust@redhat.com>
PGBackend: rename clear_state to clear_recovery_state

This is called when we complete recovery, and does not clear
all state.  clear_recovery_state is clearer.

Signed-off-by: Samuel Just <sjust@redhat.com>
ReplicatedPG: always take recovery_read_lock for recovery

Signed-off-by: Samuel Just <sjust@redhat.com>
osd/: update peer_missing and local missing if we write a degraded object

Signed-off-by: Samuel Just <sjust@redhat.com>
osd/: don't block writes on degraded objects

Signed-off-by: Samuel Just <sjust@redhat.com>
PG::purge_strays: purge peer_missing as well

Signed-off-by: Samuel Just <sjust@redhat.com>