F21 contains docker-io-1.5.0-1.fc21 (or docker-io-1.5.0-2.fc21 in updates-testing) while there's still docker-io-1.4.1-27.git76baa35.fc22 in F22
docker-io-1.5.0-18.git92e632c.fc22 has been submitted as an update for Fedora 22. https://admin.fedoraproject.org/updates/docker-io-1.5.0-18.git92e632c.fc22
Package docker-io-1.5.0-18.git92e632c.fc22: * should fix your issue, * was pushed to the Fedora 22 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing docker-io-1.5.0-18.git92e632c.fc22' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2015-3737/docker-io-1.5.0-18.git92e632c.fc22 then log in and leave karma (feedback).
docker-io-1.5.0-19.git5d7adce.fc22 has been submitted as an update for Fedora 22. https://admin.fedoraproject.org/updates/docker-io-1.5.0-19.git5d7adce.fc22
This package has changed ownership in the Fedora Package Database. Reassigning to the new owner of this component.
f22 no longer lags f21. Also, f22 has made the docker-io -> docker transition.