Add support for custom unit test directory
Add support for custom unit test directory

/tmp/test being hard-coded into ep_testsuite.cc makes it
hard to have unit tests run on ramdisks. This change allows
the unit test suite to be pointed to a dir in ramdisk.

Change-Id: I2e428ed6fe1a38513db27a70aa7a1c36bbe90c6f
Reviewed-on: http://review.couchbase.org/38379
Reviewed-by: abhinav dangeti <d73ef2279de6577f7bf081737ee47554bbb7dc82@couchbase.com>
Tested-by: Sundararaman Sridharan <333a3f71d3ad6e01fc953c4fa06bc1f3cd014910@couchbase.com>

membase/ep-engine,sriganes/ep-engine,couchbase/ep-engine,membase/ep-engine,owendCB/ep-engine,teligent-ru/ep-engine,sriganes/ep-engine,daverigby/ep-engine,membase/ep-engine,teligent-ru/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,teligent-ru/ep-engine,daverigby/kv_engine,daverigby/ep-engine,sriganes/ep-engine,hisundar/ep-engine,sriganes/ep-engine,daverigby/ep-engine,hisundar/ep-engine,daverigby/ep-engine,couchbase/ep-engine,daverigby/kv_engine,daverigby/kv_engine,owendCB/ep-engine,couchbase/ep-engine,membase/ep-engine,jimwwalker/ep-engine,jimwwalker/ep-engine,owendCB/ep-engine,owendCB/ep-engine,daverigby/kv_engine,hisundar/ep-engine,jimwwalker/ep-engine,jimwwalker/ep-engine,hisundar/ep-engine