Fix check to server migration complete test

The patch [1] added an extra check to migration complete test
waiting for the source share server to be deleted. However, this
behavior is not for all releases, only after Wallaby release. So,
this patch fixed the problem by only checking with the expected releases.

[1] https://review.opendev.org/c/openstack/manila-tempest-plugin/+/808834

Change-Id: Ic0b0773e3baa3904bc5c28307772da425f77b6de
1 file changed