Fixup check for unistd.h
Fixup check for unistd.h

Change-Id: I55411336d0ab81c2a9d33bcf854b400af9c857a9
Reviewed-on: http://review.couchbase.org/37582
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>
Tested-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

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