lib-httpd.sh: print error.log on error

Failure to bring up httpd for testing is not considered an error, so the
trash directory, which contains this error.log file, is removed and we
don't know what made httpd fail to start. Improve the situation a bit,
print error.log but only in verbose mode.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-httpd.sh

@@ -180,6 +180,7 @@ start_httpd() {
 	if test $? -ne 0
 	then
 		trap 'die' EXIT
+		cat "$HTTPD_ROOT_PATH"/error.log >&4 2>/dev/null
 		test_skip_or_die $GIT_TEST_HTTPD "web server setup failed"
 	fi
 }