t3c should use secondary parent if there is no ONLINE primary parent

[jpappa200]

This Improvement request (usability, performance, tech debt, etc.) affects these Traffic Control components:

• Traffic Control Cache Config (t3c, formerly ORT)

Current behavior:

In a MSO DS, if you have a cachegroup (mid) that has an OFFLINE primary parent (ORG), and an ONLINE secondary parent (ORG), t3c assumes that no parent exists, and hence generates the parent config without anything in it.

New behavior:

t3c should log an error/ warning noting that the primary ORG parent was OFFLINE, and then should go ahead and try the secondary parent, and update the parent config accordingly.