Post push fix.

The full group suffix was not used whan starting the "check-warning"
processes. This caused problems in a cluster setup where the full group
suffix consists of serverid.clusterid. Thus the "check-warning" failed to
get the correct configuration and couldn't connect to mysqld.

Fix by passing everything after the "group name" as --default-group-
suffix.

Also remove an extra semicolon at end of line in check-warnings.test

Change-Id: I92edcfc874b809631cca4e26d77a1fcdb48b5301