git-cvsimport: force checkout of working tree after initial import

git-cvsimport: force checkout of working tree after initial import

When creating a brand new git repository through git-cvsimport (not
incremental import), force a checkout of HEAD of master as working tree
after successful import using the -f switch to git checkout.  Otherwise
the working tree is empty, and all files are reported as 'deleted' by
git status.

This was noticed and reported by Cameron Dale through
 http://bugs.debian.org/430903

Signed-off-by: Gerrit Pape <pape@smarden.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>