btl/tcp: Skip printing error message in racy cleanup path

Avoid printing an error message about ENOTCONN return codes from
getpeername() when handling an incoming connection request.  At
this point in the receive state machine, the remote process has
been verified to be a valid OMPI instance.  In all-to-all startup
at 4k rank scale, we're seeing this error message when the remote
side drops the connection because it realizes it's the "loser"
in the connection race.  We were already doing all the right things,
other than printing a scary error message.  So skip the error
message and call it good.

Signed-off-by: Brian Barrett <bbarrett@amazon.com>

Author: bwbarrett

opal/mca/btl/tcp/btl_tcp_component.c

@@ -1515,11 +1515,13 @@ static void mca_btl_tcp_component_recv_handler(int sd, short flags, void* user)
 
     /* lookup peer address */
     if(getpeername(sd, (struct sockaddr*)&addr, &addr_len) != 0) {
-        opal_show_help("help-mpi-btl-tcp.txt",
-                       "server getpeername failed",
-                       true, opal_process_info.nodename,
-                       getpid(),
-                       strerror(opal_socket_errno), opal_socket_errno);
+        if (ENOTCONN != opal_socket_errno) {
+            opal_show_help("help-mpi-btl-tcp.txt",
+                           "server getpeername failed",
+                           true, opal_process_info.nodename,
+                           getpid(),
+                           strerror(opal_socket_errno), opal_socket_errno);
+        }
         CLOSE_THE_SOCKET(sd);
         return;
     }