skopeo.spec: drop [/var]/srv/containers from file list
Stop creating `/srv/containers` directories. Files under `/srv` are
usually owned and created by the users themselves, so owning directories
under there seems odd.
In fact, grepping through all the Fedora spec files, no other package
creates or owns anything in `/srv` apart from this package.
The SELinux file context installed by [1] will still take care of proper
labeling for the directory. This is analogous to how e.g. `/srv/www` is
correctly labeled by the policy, and HTTP servers like `httpd` and
`nginx` don't explicitly create or own `/srv/www`.
This also works around rpm-ostree currently choking on `/srv/containers`
because it falls outside the list of permitted paths.
[1] https://github.com/containers/container-selinux/pull/72