Fix except in lvm.py
Fix except in lvm.py

Consolidation of brick exceptions into a single
brick exception.py file neglected to updated files
that were using it:
    (see change I577d403f02c2fd0d727d2694776008e1e9791453)

The result is the lvm driver was doing an except on lvm.VolumeGroupNotFound
which didn't exist anymore as it's in brick/exception now.

We still need to clean up exceptions all through here, and this still
isn't handled by service init anyway, but at least with this we are
raising a valid exception.

Change-Id: I588e9ac6548823b291d284f68f6133879bf3dfbf
Fixes: bug 1216122

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