Liu 186 - Register DIM with zeroconf with MM

[pritchardn]

• Adds REST APIs for MM to add/remove DIMs & Nodes from DIMs
• Adds zeroconf discovery of DIMs
• Adds nm_dim_assigner - assigns NMs to DIMs as they come on/off-line
• Adds associated tests asserting this functionality works when zeroconf is enabled, and does not work when disabled.

Limitations:

• Does not handle multiple DIMs
• Performs no assignments with more than a single DIM

[coveralls]

Coverage decreased (-17.0%) to 64.002% when pulling 6d3d6fb on liu-186-2 into 06cd2c3 on master.

[coveralls]

Coverage increased (+0.1%) to 81.142% when pulling 3e993f3 on liu-186-2 into 06cd2c3 on master.

[rtobar]

Sorry for the delay on reviewing this, I finally got the change to give it a close look.

Overall the code looks good to me, nice to see tests going alongside the new code (and coverage going up 😄). Most changes are minor things, so hopefully it won't be too much of a burden to act on them.

[pritchardn]

Thank you for the feedback/suggestions by the way, it's very appreciated :D

[rtobar]

Just a final small detail and I'm happy to get this merged.

I found wait_until and friends a bit confusing and verbose, but (if you agree) I'll compress that a bit afterwards to not block this PR any longer.

[rtobar]

Changes look good to me, let's ignore the failure for the time being, I've addressed it in 05076f9