Fix getRefsByPrefix usage

Ie1b9ebd194a4ca2542d9aaf5c59c71dfbb361676 removed usage of the
deprecated getRefs(PREFIX) API, but missed that the returned key was
being used and the key had the prefix removed. Get ls-batches working
correctly again by stripping the prefix from the returned Ref.

Change-Id: I86784fdeb3a39e6d4ad44a75dcb57dd14c91db18
1 file changed