high: parse: Allow role in rule-based location constraints (bnc#878128)

A quirk in the structure of location constraints prevented constraints
with both role assignment and location rules from parsing correctly.

This changes the parse structure of the constraints to allow this. It
also allows the previous structure when parsing the CLI syntax, for
backwards compatibility.
Merge pull request #25 from krig/bnc878128

high: parse: Allow role in rule-based location constraints (bnc#878128)