dropped unused misc:retry

Specific reason why I'm doing it now is that test leaves messages in
process mailbox. And given it's not used anywhere it's best to just
drop this code.

Change-Id: I0772be04c83f78331e5124735a944176947d9a1c
Reviewed-on: http://review.couchbase.org/38984
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>