BUG/MINOR: session: fix some leftover from debug code

Commit 82569f91 moved the health and monitor-net checks to session.c
but a debug test introduced 0& to disable MSG_DONTWAIT in the recv()
call and this debug code remained there. Since the socket is marked
non-blocking, there should be no effect but it's dangerous to keep
such a thing here.
diff --git a/src/session.c b/src/session.c
index 3fcce84..1d5514e 100644
--- a/src/session.c
+++ b/src/session.c
@@ -151,7 +151,7 @@
 		 *  - HEALTH mode without HTTP check => just send "OK"
 		 *  - TCP mode from monitoring address => just close
 		 */
-		recv(cfd, trash, trashlen, 0&MSG_DONTWAIT);
+		recv(cfd, trash, trashlen, MSG_DONTWAIT);
 		if (p->mode == PR_MODE_HTTP ||
 		    (p->mode == PR_MODE_HEALTH && (p->options2 & PR_O2_CHK_ANY) == PR_O2_HTTP_CHK))
 			send(cfd, "HTTP/1.0 200 OK\r\n\r\n", 19, MSG_DONTWAIT|MSG_NOSIGNAL|MSG_MORE);