ctld: Be more consistent for auth parameters in the UCL config

[jhb]

Summary

The auth-group required an array of entries for "chap", "chap-mutual",
"initiator-name", and "initiator-portal" whereas the target context
required exactly one entry (and only permitted a single entry).

Allow either a single entry or an array of entries for these keywords
in both the auth-group and target contexts.

[jhb]

Rebase after removing globals from parse.y