checkout: fix regression in checkout -b on intitial checkout
When doing a 'checkout -b' do a full checkout including updating the working
tree when doing the initial checkout. As the new test involves an filesystem
access, do it later in the sequence to give chance to other cheaper tests to
leave early. This fixes the regression in behavior caused by
fa655d8411
(checkout: optimize "git checkout -b <new_branch>", 2018-08-16).
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>