CBQE-1531: add concurrent queries test for tuq

Change-Id: If5bba42ddaabc139d857179933ea788579ff5d02
Reviewed-on: http://review.couchbase.org/29411
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>