Better differentiate duplicate errnos

[jrconlin]

we have several instances where we return the exact same codes for very different reasons.

For instance, a 410:106 means:

• a router is not recognized
• a subscription does not have a "current_month" in the UAID record
• the current month is not in the list of db message tables
• the channelID is not in the list of valid channels for the UAID

When trying to determine why we report a subscription as invalid, or attempting to debug a possible problem, it'd be useful to be able to differentiate these.