Reconfiguring named using RNDC is a common action in BIND 9 system
tests. It involves sending the "reconfig" RNDC command to a named
instance and waiting until it is fully processed. Add a reconfigure()
method to the NamedInstance class in order to simplify and standardize
named reconfiguration using RNDC in Python-based system tests.
TODO:
- full reconfiguration support (w/templating *.in files)
- add an "rndc null" before every reconfiguration to show which file
is used (NamedInstance.add_mark_to_log() as it may be generically
useful?)
(cherry picked from commit fdc45c70e8)