Catch std::bad_alloc in Audit::add_to_filleventqueue
Catch std::bad_alloc in Audit::add_to_filleventqueue

Catch allocation failures for new events to be added to the
audit trail and (try) to log the event to the log and
increment the number of dropped events (which ns_server
polls)

Change-Id: I25ae2e14460803abc91db9311ba895a90bef06fd
Reviewed-on: http://review.couchbase.org/98184
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Paolo Cocchi <9dd88c9f3e5cbab6e19a6c020f107e0c648ac956@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine