[horizon] VNC console fails after instance migration

Steps
1. Deploy cluster with at least 2 computes, set Ceph for Ephemeral volumes.
2. Launch 3 TestVM instances: VM-1, VM-2, VM-3.
3. Open Instance VNC Console via Horizon for every instance.
4. Migrate 1st instance:
nova migrate VM-1
nova resize-confirm VM-1
5. Live migrate 3rd instance:
nova live-migration VM-3 node-3.test.domain.local

Do not migrate remaining 2nd instance just to compare.

7. Open VNC consoles for each instance one more time. See minimized view of consoles.
8. Click on link "Click here to show only console"
9. Try to type any commands into instances VNC consoles.
Expected that console will work.
Actual result: console freezed (but cursor still blinks) in its last state before instance migration. And it ignores any attempts to type commands into it.
Console continues to work properly only for not migrated instance.

Bug found on 8.0 RTM iso
VERSION:
  feature_groups:
    - mirantis
  production: "docker"
  release: "8.0"
  api: "1.0"
  build_number: "570"
  build_id: "570"
  fuel-nailgun_sha: "558ca91a854cf29e395940c232911ffb851899c1"
  python-fuelclient_sha: "4f234669cfe88a9406f4e438b1e1f74f1ef484a5"
  fuel-agent_sha: "658be72c4b42d3e1436b86ac4567ab914bfb451b"
  fuel-nailgun-agent_sha: "b2bb466fd5bd92da614cdbd819d6999c510ebfb1"
  astute_sha: "b81577a5b7857c4be8748492bae1dec2fa89b446"
  fuel-library_sha: "c2a335b5b725f1b994f78d4c78723d29fa44685a"
  fuel-ostf_sha: "3bc76a63a9e7d195ff34eadc29552f4235fa6c52"
  fuel-mirror_sha: "fb45b80d7bee5899d931f926e5c9512e2b442749"
  fuelmenu_sha: "78ffc73065a9674b707c081d128cb7eea611474f"
  shotgun_sha: "63645dea384a37dde5c01d4f8905566978e5d906"
  network-checker_sha: "a43cf96cd9532f10794dce736350bf5bed350e9d"
  fuel-upgrade_sha: "616a7490ec7199f69759e97e42f9b97dfc87e85b"
  fuelmain_sha: "d605bcbabf315382d56d0ce8143458be67c53434"