ReplicatedPG: assert build_push_op succeeds on primary

Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG: fix prep_push_to_replica debug output

Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG: we need to update recovery_info in on_local_recover

For lost_unfound.

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