CBQE-0: fix warmuptest

    m, v, r = self.request_map(self.rest , self.bucket)
  File "lib/memcached/helper/data_helper.py", line 792, in request_map
    self.add_memcached(replica, memcacheds, rest, bucket)
  File "lib/memcached/helper/data_helper.py", line 818, in add_memcached
    raise ex
ValueError: filedescriptor out of range in select()

http://qa.hq.northscale.net/view/All/job/centos_x64--00_04--warmup-P0/20/consoleFull

Change-Id: Ie9d9ee814284ff618fe30085b17073bb3fab1205
Reviewed-on: http://review.couchbase.org/34887
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>