CP-5818: [UnitTest] Remove volume activation related unit tests

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CA-129230: [UnitTest] Fix unit tests

Serialisation of a class name has changed over the python versions, so
the test needed to be adjusted. Now only the error message is searched
in the log instead of expecting a full match.

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CP-8744 & CP-5818: [UnitTest] remove LVM activate argument

Suggested-by: Thanos Makatos <thanos.makatos@citrix.com>
Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>