Lazy log the fixed_key warnings
Lazy log the fixed_key warnings

Cinder currently spews quite a bit of WARNINGs like this with
the default settings:

WARNING cinder.keymgr.conf_key_mgr [-] config option keymgr.fixed_key
has not been defined: some operations may fail unexpectedly

Many users may not be using features that require key manager...
so logging the WARNING message a bit more lazily seems reasonable.

Change-Id: I5ab72285c7d4bc2ec3196dd94fabf977b3a4ebaf
Closes-bug: 1252512

NeCTAR-RC/cinder,julianwang/cinder,tlakshman26/cinder-https-changes,Paul-Ezell/cinder-1,Accelerite/cinder,sasukeh/cinder,nikesh-mahalka/cinder,Akrog/cinder,JioCloud/cinder,phenoxim/cinder,Nexenta/cinder,Accelerite/cinder,apporc/cinder,NetApp/cinder,cloudbase/cinder,bswartz/cinder,rakeshmi/cinder,NeCTAR-RC/cinder,eharney/cinder,Paul-Ezell/cinder-1,mahak/cinder,github-borat/cinder,JioCloud/cinder,alex8866/cinder,winndows/cinder,phenoxim/cinder,Akrog/cinder,j-griffith/cinder,nexusriot/cinder,Datera/cinder,CloudServer/cinder,takeshineshiro/cinder,takeshineshiro/cinder,julianwang/cinder,Thingee/cinder,tlakshman26/cinder-https-changes,dims/cinder,openstack/cinder,dims/cinder,duhzecca/cinder,Nexenta/cinder,bswartz/cinder,spring-week-topos/cinder-week,petrutlucian94/cinder,manojhirway/ExistingImagesOnNFS,nikesh-mahalka/cinder,rakeshmi/cinder,scality/cinder,Hybrid-Cloud/cinder,scality/cinder,abusse/cinder,Thingee/cinder,github-borat/cinder,alex8866/cinder,Thingee/cinder,potsmaster/cinder,potsmaster/cinder,hguemar/cinder,saeki-masaki/cinder,hguemar/cinder,tlakshman26/cinder-new-branch,manojhirway/ExistingImagesOnNFS,leilihh/cinder,tlakshman26/cinder-bug-fix-volume-conversion-full,redhat-openstack/cinder,abusse/cinder,openstack/cinder,redhat-openstack/cinder,winndows/cinder,spring-week-topos/cinder-week,blueboxgroup/cinder,tlakshman26/cinder-bug-fix-volume-conversion-full,j-griffith/cinder,scottdangelo/RemoveVolumeMangerLocks,apporc/cinder,cloudbase/cinder,Datera/cinder,leilihh/cinder,saeki-masaki/cinder,Hybrid-Cloud/cinder,tlakshman26/cinder-new-branch,ge0rgi/cinder,scottdangelo/RemoveVolumeMangerLocks,CloudServer/cinder,sasukeh/cinder,blueboxgroup/cinder,mahak/cinder,NetApp/cinder,petrutlucian94/cinder,duhzecca/cinder,eharney/cinder,nexusriot/cinder