Added -p option to run selected engine_test without forking.
Added -p option to run selected engine_test without forking.

Signed-off-by: Vandana Shah <e8ef6bf8167176b52453793987ce7a4a0f6d30eb@zynga.com>

zbase/memcached,zbase/memcached,zbase/memcached,zbase/memcached,zbase/memcached