Remove temporary debugging printf that was used to detect the presence

of a race that had previously caused a panic in order to determine if
the fix was for the right problem.  It was.

MFC after:	2 weeks

sys/kern/uipc_usrreq.c

@@ -907,10 +907,6 @@ unp_connect(so, nam, td)
 	UNP_LOCK();
 	unp = sotounpcb(so);
 	if (unp == NULL) {
-		/*
-		 * XXXRW: Temporary debugging printf.
-		 */
-		printf("unp_connect(): lost race to another thread\n");
 		error = EINVAL;
 		goto bad2;
 	}