Merge branch 'jk/prune-packed-server-info'

Fix recent breakage in Git 2.2 that started creating info/refs and
objects/info/packs files with permission bits tighter than user's
umask.

* jk/prune-packed-server-info:
update-server-info: create info/* with mode 0666
t1301: set umask in reflog sharedrepository=group test