PG: check_recovery_sources must happen even if not active

missing_loc/missing_loc_sources also must be cleaned up
if a peer goes down during peering:

1) pg is in GetInfo, acting is [3,1]
2) we find object A on osd [0] in GetInfo
3) 0 goes down, no new peering interval since it is neither up nor
acting, but peer_missing[0] is removed.
4) pg goes active and try to pull A from 0 since missing_loc did not get
cleaned up.

Backport: bobtail
Fixes: #4371
Signed-off-by: Samuel Just <sam.just@inktank.com>