HA. OSTF tests fail & neutron l3 angent stops on primary controller after connection loss on management nic.

Scenario:
1. Deploy HA env using 5.1.1 48-RC2 iso:
with neutron GRE, ceph for images and volumes. 3x Controllers, 2x computes, 2x ceph-storage
2. Run Network verification tests (passes well)
3. Run OSTF (all pass fine)
4. Simulate connection loss on management interface of the primary controller node
by running next command
# brctl delif <br> <if>
where 'if' is the node interface attached to management network
and 'br' is the bridge this 'if' is attached to.
5. Wait for 30+ min
6. Run OSTF

Result:
None of the test passes.

OSTF logs contain multiple "Service Unavailable (HTTP 503)" errors

also crm status says, that l3 agent is stopped on primary controller.

Cluster stays quite operational though.