rbd: Move the encryption check in build
rbd: Move the encryption check in build

No sense opening a connection only to fail because we don't support the
type of build being attempted.

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

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