Instead of mutating and reverting, just create a copy and pass the copy
around.
Add a unit test for builder dispatcher.run
Fix two test failures
Fix image history by adding a CreatedBy to commit options. Previously the
createdBy field was being created by modifying a reference to the runConfig that
was held from when the container was created.
Fix a test that expected a trailing slash. Previously the runConfig was being
modified by container create. Now that we're creating a copy of runConfig
instead of sharing a reference the runConfig retains the trailing slash.
Signed-off-by: Daniel Nephin <dnephin@docker.com>
