Add ID-mapping tests
Add ID-mapping tests

Add tests that exercise the ID mapping, diff applying, and diff
generating code against layers which are created with assorted ID
mapping options, and verify that layer contents also follow the expected
rules when we create containers.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

rhatdan/storage,containers/storage,rhatdan/storage,containers/storage,containers/storage,rhatdan/storage