Fix for api_test.go
Fix for api_test.go

This passed in the #744 before merge, but apparently the test changed
since the PR was created in ways that led to a new failures.

Signed-off-by: Aaron Lehmann <8ecfc6017a87905413dcd7d63696a2a4c351b604@docker.com>

thaJeztah/distribution,thaJeztah/distribution