MB-100: handle 'unable to resolve host' in docloadertest

http://qa.hq.northscale.net/view/2.0.1/job/ubuntu-32-2.0-single-node/483/consoleFull

Change-Id: If3b63c74093c8a387fd76192ea5d157067d5d746
Reviewed-on: http://review.couchbase.org/24822
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>