libceph: kill bad_proto ceph connection op

(cherry picked from commit 6384bb8b8e88a9c6bf2ae0d9517c2c0199177c34)

No code sets a bad_proto method in its ceph connection operations
vector, so just get rid of it.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>