Fix the test to determine if we could restart memcached

rest.diag_eval returns two values

Change-Id: If9be01ae38ed297edede759c66d458f3b931faf8
Reviewed-on: http://review.couchbase.org/33805
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>