Tests: made sure grpc pending control frames are sent.

This extends a previously committed test in ea00c5b.  Specifically,
this ensures that a SETTINGS frame received from backend after the
whole request has been proxied, should be eventually acknowledged.

Author: pluknet

grpc.t

@@ -24,7 +24,7 @@ select STDERR; $| = 1;
 select STDOUT; $| = 1;
 
 my $t = Test::Nginx->new()->has(qw/http rewrite http_v2 grpc/)
-	->has(qw/upstream_keepalive/)->plan(146);
+	->has(qw/upstream_keepalive/)->plan(147);
 
 $t->write_file_expand('nginx.conf', <<'EOF');
 
@@ -208,6 +208,10 @@ $frames = $f->{http_end}();
 ($frame) = grep { $_->{type} eq "HEADERS" } @$frames;
 ok($c = $frame->{headers}{'x-connection'}, 'keepalive 2 - connection');
 
+$frames = $f->{read_settings}();
+($frame) = grep { $_->{type} eq "SETTINGS" } @$frames;
+is($frame->{flags}, 1, 'pending frames acked');
+
 $frames = $f->{http_start}('/KeepAlive', reuse => 1);
 ($frame) = grep { $_->{type} eq "HEADERS" } @$frames;
 ok($frame, 'upstream keepalive reused');
@@ -769,6 +773,9 @@ reused:
 	$f->{settings} = sub {
 		$c->h2_settings(@_);
 	};
+	$f->{read_settings} = sub {
+		return $c->read(all => [{ type => 'SETTINGS' }]);
+	};
 	$f->{goaway} = sub {
 		$c->h2_goaway(@_);
 	};