Avoid conflicts with other tests instances

Avoid conflicts with other instances that exist, for example when
weren't deleted in other tests. Just filter out them in test that
check instances amount by server IDs

Closes-Bug: #1340382
Change-Id: I51494c9f47745810583f682caadcd8772805733a
Skip telemetry_notification_api test due to bug 1336755

Temporarily skip the nova notification test due to the frequency
of timeouts in the gate, pending a fix for bug LP #1336755.

Related-Bug: 1336755

Change-Id: Ie0eef11998f4647a3e187b357630d9531a6cf1e8
Merge "Avoid conflicts with other tests instances"
Merge "Skip telemetry_notification_api test due to bug 1336755"