storage: Add extra failure condition for luks volume creation
storage: Add extra failure condition for luks volume creation

Commit id '5e46d7d6' did not take into account that usage of a luks
volume will require usage of the master key encrypted passphrase for
a QEMU environment.  So rather than allow creation of something that
won't be usable, just fail the creation.

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