storage: Alter error message in probe/empty checks
storage: Alter error message in probe/empty checks

For case VIR_STORAGE_BLKID_PROBE_DIFFERENT, clean up the message to
avoid using the virsh like --overwrite syntax. Additionally provide
a different error message when not writing the label to avoid confusion.

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