Add fake implementations of:
- is_selinux_enabled
- security_disable
- selinux_virtual_domain_context_path
- selinux_virtual_image_context_path
- selinux_lxc_contexts_path
- selabel_open
- selabel_close
- selabel_lookup_raw
The selabel_* functions back onto the real implementations if SELinux is
enabled on the test system, otherwise we just implement a fake selabel
handle which errors out on all labelling lookups.
With these changes in place, securityselinuxtest and
securityselinuxlabeltest don't need to skip all tests if SELinux isn't
available; they can exercise much of the security manager code.
Signed-off-by: Michael Chapman <mike@very.puzzling.org>
