netmodelsTests: Test IPv6.validateAddress and IPv6.validatePrefixlen

Use addresses with prefixes to test the latter function.

Change-Id: I9e39fd9d36f5ceb4967b41d611faa8eedcfe3e1b
Signed-off-by: Ondřej Svoboda <osvoboda@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29906
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>