JMembaseTest: Disable 'unknown host' test

This test takes a potentially long time on DNS servers which
redirect or 'blackhole' an NXDOMAIN response to something else.

Change-Id: I07bd21da9e17a92db57af11c938476ccf961dd9c
Reviewed-on: http://review.couchbase.org/38530
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>