MB-9690: Increase timeout for get operation from 5 to 15 seconds

Change-Id: I9af83296f7d5f53be56b584c22ec64947a06145b
Reviewed-on: http://review.couchbase.org/30908
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>