Fix TypeError in QoSBandwidthAndPacketRateTests

[1] Added random int to flavor name but that resulted into
TypeError: can only concatenate str (not "int") to str.

Concatenate using % operator to fix it.

Also make tempest-full-ussuri-py3 job non-voting temporary
to unblock gate, can be reverted once [2] is fixed.

[1] https://review.opendev.org/c/openstack/tempest/+/826946
[2] https://launchpad.net/bugs/1959600

Related-Bug: #1959467
Change-Id: I76e15b6b52bb44fec550ead510186c644c4a1c7f
2 files changed