storage_backend_rbd: fix typos
storage_backend_rbd: fix typos

s/failed/failed to

Signed-off-by: Chen Hanxiao <818f8a165c25fa146ecad28e2ef3e3fb996fa364@gmail.com>

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