MB-18462: Reduce buffer sizes to avoid stack exhaustion
MB-18462: Reduce buffer sizes to avoid stack exhaustion

Context:
tests/functional/fdb_extended_test.cc

Change-Id: I5a899ffe82f0b572245fe602e46c4a3a84945421
Reviewed-on: http://review.couchbase.org/62066
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

hisundar/forestdb,wurikiji/forestdb,couchbase/forestdb,wurikiji/forestdb,hisundar/forestdb,couchbase/forestdb