storage: Split out a helper for encryption checks
storage: Split out a helper for encryption checks

Split out a helper from virStorageBackendCreateQemuImgCmdFromVol
to check the encryption - soon a new encryption sheriff will be
patroling and that'll mean all sorts of new checks.

Signed-off-by: John Ferlan <87558058f6f829e5ec976c8ef960720af4ff9c7d@redhat.com>

crobinso/libvirt,eskultety/libvirt,nertpinx/libvirt,zippy2/libvirt,fabianfreyer/libvirt,zippy2/libvirt,fabianfreyer/libvirt,datto/libvirt,libvirt/libvirt,eskultety/libvirt,datto/libvirt,fabianfreyer/libvirt,datto/libvirt,olafhering/libvirt,jardasgit/libvirt,libvirt/libvirt,zippy2/libvirt,jardasgit/libvirt,taget/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,olafhering/libvirt,libvirt/libvirt,VenkatDatta/libvirt,datto/libvirt,eskultety/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,eskultety/libvirt,taget/libvirt,jardasgit/libvirt,nertpinx/libvirt,crobinso/libvirt,crobinso/libvirt,nertpinx/libvirt,zippy2/libvirt,taget/libvirt,jfehlig/libvirt,olafhering/libvirt,crobinso/libvirt,olafhering/libvirt,taget/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,nertpinx/libvirt,libvirt/libvirt,eskultety/libvirt,nertpinx/libvirt,datto/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,jardasgit/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,taget/libvirt,jfehlig/libvirt,jfehlig/libvirt,VenkatDatta/libvirt