Fix multi-repository support by properly respecting 'enabled' flag.
This will read the REPOS_DIR env/config setting (default is /etc/pkg
and /usr/local/etc/pkg/repos) and use the last enabled repository.
This can be changed in the environment using a comma-separated list,
or in /usr/local/etc/pkg.conf with JSON array syntax of:
REPOS_DIR: ["/etc/pkg", "/usr/local/etc/pkg/repos"]
Approved by: bapt (mentor)