Enable SO_LINGER to the so_reuseport_lb_test regression tests, preventing

many sockets in TIME_WAIT state at the end of the test.

PR:		249885
Reviewed by:	markj
Approved by:	markj
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D26549

tests/sys/netinet/so_reuseport_lb_test.c

@@ -54,6 +54,7 @@ lb_simple_accept_loop(int domain, const struct sockaddr *addr, int sds[],
 	size_t i;
 	int *acceptcnt;
 	int csd, error, excnt, sd;
+	const struct linger lopt = { 1, 0 };
 
 	/*
 	 * We expect each listening socket to accept roughly nconns/nsds
@@ -73,6 +74,10 @@ lb_simple_accept_loop(int domain, const struct sockaddr *addr, int sds[],
 		ATF_REQUIRE_MSG(error == 0, "connect() failed: %s",
 		    strerror(errno));
 
+		error = setsockopt(sd, SOL_SOCKET, SO_LINGER, &lopt, sizeof(lopt));
+		ATF_REQUIRE_MSG(error == 0, "Setting linger failed: %s",
+		    strerror(errno));
+
 		/*
 		 * Poll the listening sockets.
 		 */