ref/stream/manager: Fix test flake where a conn was left open on error.

Change-Id: Ibb262438eb02b489c3012163f8b10e6d7feb24a2
diff --git a/runtime/internal/rpc/stream/manager/manager.go b/runtime/internal/rpc/stream/manager/manager.go
index 4ddef8c..0898ad4 100644
--- a/runtime/internal/rpc/stream/manager/manager.go
+++ b/runtime/internal/rpc/stream/manager/manager.go
@@ -163,6 +163,12 @@
 	case result := <-ch:
 		conn, err = result.conn, result.err
 	case <-ctx.Done():
+		go func() {
+			result := <-ch
+			if result.conn != nil {
+				result.conn.Close()
+			}
+		}()
 		return nil, verror.New(stream.ErrDialFailed, ctx, err)
 	}
 	if err != nil {