EPIPE is a documented errno in tcp(7) on linux

Fixes: #2582

lib/libvarnish/vtcp.c

@@ -567,7 +567,7 @@ VTCP_Check(int a)
 {
 	if (a == 0)
 		return (1);
-	if (errno == ECONNRESET || errno == ENOTCONN)
+	if (errno == ECONNRESET || errno == ENOTCONN || errno == EPIPE)
 		return (1);
 #if (defined (__SVR4) && defined (__sun)) || defined (__NetBSD__)
 	/*
@@ -575,7 +575,7 @@ VTCP_Check(int a)
 	 * connection.
 	 * This is a bug in Solaris and documented behaviour on NetBSD.
 	 */
-	if (errno == EINVAL || errno == ETIMEDOUT || errno == EPIPE)
+	if (errno == EINVAL || errno == ETIMEDOUT)
 		return (1);
 #elif defined (__APPLE__)
 	/*