Perform duplicate name checks when creating things
Perform duplicate name checks when creating things

In the mall structure, check for duplicate names and IDs when creating
layers, images, and containers.  Names and IDs are shared among all
three types of data, so check all three for collisions.

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

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