ncm-named: fix retrieval of named root directory from sysconfig

Fixes #241

Wait for more unit tests to be added before merging this PR.
I don't think this is the right approach, and will break someone who has this in their sysconfig file:

 # revert our custom value and use default
 #ROOTDIR = /my/custom/location

The root cause here seems to be that the previous regexp was not correctly ignoring commented lines at line 136. According to the [rhel6 guide](https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/s1-BIND.html) the default location remains /etc/named.conf