Remove meaningless volume negative test

The removed negative test verified NotFound exception even if
passing invalid format value on URI with GET method.
The test is duplicated with test_volume_get_nonexistent_volume_id.
It doesn't have any value actually, and it is nice to remove
it from the integration test suite: Tempest.

NOTE: There is a similar test test_get_volume_without_passing_volume_id
      but we keep it at this time because the REST operation is like
        GET os-volumes/
      and it seems a general operation and it has some merit.

Change-Id: I7c99f61dc54ef7c437c7e4574eba935d76ef9318
1 file changed