MB-100: catch BaseException at the end of all exps

Change-Id: I53e0b6ef98ce488f00fbe6ab2af877b0bd9cee86
Reviewed-on: http://review.couchbase.org/24814
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>