Don't prevent grow actions on devices with no max size.
Make minSize, maxSize consistent and correct.

StorageDevice defaults should be dependent on whether the device is
resizable -- not whether or not the format has known size limits.

Any minSize or maxSize may be zero, meaning there is no known limit.
Don't corrupt the environment when setting up StorageTestCase.

Also adds some necessary patching to PartitionDevice related to resize
so that it does not require setting up a mocked parted.Geometry.
Update action_test.py to specify sizes using blivet.size.Size.
Get action_test into working order.