ep_perfsuite: Reduce ITERATIONS for Debug builds
ep_perfsuite: Reduce ITERATIONS for Debug builds

Similary to TSan / ASan, run with a reduced iteration count under
Debug builds to speed runtime.

Change-Id: Ib480dbe6b75ed02af1667d684c11a090cb4cf81e
Reviewed-on: http://review.couchbase.org/112924
Reviewed-by: Ben Huddleston <6c0d3f0e87b08a8c49786ca528f2c4b1ad3d36f3@couchbase.com>
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine