Implemented missing support for DNSMASQ_LISTENING environment variable

[dhutchison]

Documentation included reference to a "DNSMASQ_LISTENING" environment variable which could be supplied to the docker container to change the DNSMASQ listening behaviour, this was not implemented in the start script so had not effect. This change implements updating the setupVars configuration file based on the environment variable value.

Description

Change to the setup_dnsmasq function in bash_functions to take an additional parameter for the DNSMASQ_LISTENING environment variable value. If this is a non-empty string the DNSMASQ_LISTENING setting will be written to the setupVars.conf configuration file.

Motivation and Context

Fixes feature noted in the documentation which is missing.

How Has This Been Tested?

Manual testing has been performed against the amd_64 version of the image (changes are version agnostic), checking that the environment variable values of "all" and "local" make the appropriate change to the settings displayed in the "DNS" tab of the admin web interface. Confirmed no environment variable supplied functions as before.

Types of changes

• [x ] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x ] My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[diginc]

Looks good, Thanks! I didn't quite get where this variable was used at first (thought it was dnsmasq daemon at first). Sorry for the delay. I'll get this built into a dev image right away for you to test.