WIP: [#130] Improve rndc usage
Improve how we use rndc in Stork agent. Rather than assuming there is a rndc.key file in a default location, look up the control port, control address and secret key in the named configuration file.
Add a parameter to the AppBind9 structure that is the controller for sending commands. This can now be mocked in the unit tests.
Closes #130 (closed)
Closes #131 (closed)