* Create a git-sync user to run as, with an entry in /etc/passwd and
writable homedir
* Remove our own validation of key perms - let SSH do that.
* Update docs,
Add an option to specify a git http cookie file in the k8s yaml
that will be configured as the global git cookie file in the git-sync
client.
This is a useful access mechanism for some some hosted repositories
where SSH and passwords are not easily available, such as Google Cloud
Source Repositories.