CBQE-1779, CBQE-1785: Added tests for online upgrade, incremental_upgrade, and some minor fixes

Change-Id: Ic29fa6499dd9d4aba300cf1b054914d8a5cc13a3
Reviewed-on: http://review.couchbase.org/31200
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>