Add retry function for Docker keyring
Add retry function for Docker keyring

Sometimes the keyserver has a mirror failure which results in a failed
gate. Add a retry to help prevent that failure.

TrivialFix

Change-Id: I143626dd6d799b4ea0f82f6649d2155c2f45a115

stackforge/kolla,nihilifer/kolla,nihilifer/kolla,mrangana/kolla,openstack/kolla,toby82/kolla,dardelean/kolla-ansible,mandre/kolla,coolsvap/kolla,stackforge/kolla,negronjl/kolla,intel-onp/kolla,stackforge/kolla,rahulunair/kolla,negronjl/kolla,toby82/kolla,GalenMa/kolla,openstack/kolla,intel-onp/kolla,mrangana/kolla,coolsvap/kolla,tonyli71/kolla,toby82/kolla,rahulunair/kolla,mandre/kolla,coolsvap/kolla,mandre/kolla,dardelean/kolla-ansible,dardelean/kolla-ansible,tonyli71/kolla,GalenMa/kolla,negronjl/kolla