bgp/socket: Make BGP error message slightly more useful.

Also, don't warn about missing BINDTODEVICE on BSD.  It simply
isn't supported there, so no need to fill logs with warnings users
can do nothing about.

Signed-off-by: Ben Greear <greearb@candelatech.com>

xorp/bgp/xrl_target.cc

@@ -116,7 +116,7 @@ XrlBgpTarget::bgp_0_3_local_config(
     ** We may already be configured so don't allow a reconfiguration.
     */
     if(!_awaiting_config)
-	return XrlCmdError::COMMAND_FAILED("Attempt to reconfigure BGP");
+	return XrlCmdError::COMMAND_FAILED("Attempt to reconfigure BGP denied.");
 
     _use_4byte_asnums = use_4byte_asnums;
     try {

xorp/libcomm/comm_sock.c

@@ -1137,8 +1137,13 @@ comm_set_bindtodevice(xsock_t sock, const char * my_ifname)
 
     return (XORP_OK);
 #else
+#ifndef __FreeBSD__
+    // FreeBSD doesn't implement this, so no use filling logs with errors that can't
+    // be helped.  Assume calling code deals with the error code as needed.
     XLOG_ERROR("setsockopt SO_BINDTODEVICE %s: %s",
 	       my_ifname, "SO_BINDTODEVICE support not present.");
+#endif
+    UNUSED(my_ifname);
     UNUSED(sock);
     return (XORP_ERROR);
 #endif