Dashboard Blacklist prefixes could match any number

The way the code is written in dashboard to ignore extension ranges is designed in a way where-as it only checks the prefix. So in Zulu's case the prefix of the extensions are 90XXXXX therefore a user could have extensions 900-909, this creates zulu extensions 90900 - 90909 but the code matches 90900 - 90909 AND 900-909 so nothing would ever be shown. This should be improved and I'm deeming it a bug.

Modules that call this function should just return all extensions they are controlling instead of some random prefix to save 2ms of processing time.