xprtrdma: disconnect and flush cqs before freeing buffers

Otherwise a FRMR completion can cause a touch-after-free crash.

In xprt_rdma_destroy(), call rpcrdma_buffer_destroy() only after calling
rpcrdma_ep_destroy().

In rpcrdma_ep_destroy(), disconnect the cm_id first which should flush the
qp, then drain the cqs, then destroy the qp, and finally destroy the cqs.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index 64443eb..41e452b 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -270,8 +270,8 @@
 
 	xprt_clear_connected(xprt);
 
-	rpcrdma_buffer_destroy(&r_xprt->rx_buf);
 	rpcrdma_ep_destroy(&r_xprt->rx_ep, &r_xprt->rx_ia);
+	rpcrdma_buffer_destroy(&r_xprt->rx_buf);
 	rpcrdma_ia_close(&r_xprt->rx_ia);
 
 	xprt_rdma_free_addresses(xprt);