ReplicatedPG: replace clean_up_local with a debug check

ReplicatedPG: replace clean_up_local with a debug check

Stray objects should have been cleaned up in the merge_log
transactions.  Only on the primary have those operations
necessarily been flushed at activate().

Fixes: 5084
Signed-off-by: Samuel Just <sam.just@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 278c7b59228f614addf830cb0afff4988c9bc8cb)