libceph: fix messenger retry

In ancient times, the messenger could both initiate and accept connections.
An artifact if that was data structures to store/process an incoming
ceph_msg_connect request and send an outgoing ceph_msg_connect_reply.
Sadly, the negotiation code was referencing those structures and ignoring
important information (like the peer's connect_seq) from the correct ones.

Among other things, this fixes tight reconnect loops where the server sends
RETRY_SESSION and we (the client) retries with the same connect_seq as last
time.  This bug pretty easily triggered by injecting socket failures on the
MDS and running some fs workload like workunits/direct_io/test_sync_io.

Signed-off-by: Sage Weil <sage@inktank.com>
diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 478f814..cfb1bbd 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -172,16 +172,8 @@
 
 	/* connection negotiation temps */
 	char in_banner[CEPH_BANNER_MAX_LEN];
-	union {
-		struct {  /* outgoing connection */
-			struct ceph_msg_connect out_connect;
-			struct ceph_msg_connect_reply in_reply;
-		};
-		struct {  /* incoming */
-			struct ceph_msg_connect in_connect;
-			struct ceph_msg_connect_reply out_reply;
-		};
-	};
+	struct ceph_msg_connect out_connect;
+	struct ceph_msg_connect_reply in_reply;
 	struct ceph_entity_addr actual_peer_addr;
 
 	/* message out temps */