libceph: use CEPH_AUTH_UNKNOWN in ceph_auth_build_hello()

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/auth.c

@@ -114,7 +114,7 @@ int ceph_auth_build_hello(struct ceph_auth_client *ac, void *buf, size_t len)
 	monhdr->session_mon = cpu_to_le16(-1);
 	monhdr->session_mon_tid = 0;
 
-	ceph_encode_32(&p, 0);  /* no protocol, yet */
+	ceph_encode_32(&p, CEPH_AUTH_UNKNOWN);  /* no protocol, yet */
 
 	lenp = p;
 	p += sizeof(u32);