Make rabbitmq user and vhost name shorter in kuttl tests

Some recent change (maybe [1a)], the string used in infra-operator for
rabbitmquser creation has changed from
`nova-kuttl-notification-transport-nova-notifications-user`
to `rabbitmq-notifications-nova-notifications-user-nova-notifications`
which is longer that 63 char openshift limit, leading to error:

RabbitMQ user error occurred Secret "rabbitmq-user-rabbitmq-notifications-nova-notifications-user-nova-notifications" is invalid: metadata.labels: Invalid value: "rabbitmq-notifications-nova-notifications-user-nova-notifications": must be no more than 63 characters

While this may be understood as a bug, this patch is making vhost and user names
shorter to unblock the kuttl test.

[1] openstack-k8s-operators/infra-operator@fcc8556#diff-627c3e6f14aec9dd16405a764cf2e60199490e15a399bd3df182df26f00e999d

Signed-off-by: Alfredo Moralejo <amoralej@redhat.com>

Author: amoralej

test/kuttl/test-suites/default/rmquser-vhost/01-deploy.yaml

@@ -10,5 +10,5 @@ spec:
     vhost: nova-rpc
   notificationsBus:
     cluster: rabbitmq-notifications
-    user: nova-notifications
-    vhost: nova-notifications
+    user: nova-notif
+    vhost: nova-notif