t7610: don't use test_config in a subshell

test_config uses test_when_finished to reset the configuration after the test, but this does not work inside a subshell. This does not cause a problem here because the first thing the next test does is to set this config variable itself, but we are about to add a check that will complain when test_when_finished is used in a subshell. In this case, "subdir" not a submodule so test_config has the same effect when run at the top level and can simply be moved out of the subshell. Signed-off-by: John Keeping <john@keeping.me.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>