BUG/MEDIUM: connections: Don't forget to decrement idle connection counters.

In conn_backend_get(), when we manage to get an idle connection from the
current thread's pool, don't forget to decrement the idle connection
counters, or we may end up not reusing connections when we could, and/or
killing connections when we shouldn't.
diff --git a/src/backend.c b/src/backend.c
index 96d8d17..8f81c61 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1095,8 +1095,10 @@
 	/* If we found a connection in our own list, and we don't have to
 	 * steal one from another thread, then we're done.
 	 */
-	if (conn)
-		return conn;
+	if (conn) {
+		i = tid;
+		goto fix_conn;
+	}
 
 	/* Lookup all other threads for an idle connection, starting from tid + 1 */
 	for (i = tid; !found && (i = ((i + 1 == global.nbthread) ? 0 : i + 1)) != tid;) {
@@ -1116,6 +1118,7 @@
 	if (!found)
 		conn = NULL;
 	else {
+fix_conn:
 		conn->idle_time = 0;
 		_HA_ATOMIC_SUB(&srv->curr_idle_conns, 1);
 		_HA_ATOMIC_SUB(&srv->curr_idle_thr[i], 1);