Add __hash__ to RecordSet to allow python3 hash key/set use

[ross]

Ran into this problem with the Azure DNS provider when updating octoDNS to support Python 3 in https://github.com/github/octodns/pull/384. It looks like objects that implement __eq__ in Python 3 are also required to implement a custom __hash__ method to match. RecordSet in azure-mgmt-dns==3.0.0 inherits from Model leading to:

(env3)otter:octodns ross$ ./script/coverage tests/test_octodns_provider_azuredns.py 2>&1 | tee /tmp/run.log
....E....
======================================================================
ERROR: test_populate_records (test_octodns_provider_azuredns.TestAzureDnsProvider)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ross/github/octodns/tests/test_octodns_provider_azuredns.py", line 449, in test_populate_records
    exists = provider.populate(zone)
  File "/Users/ross/github/octodns/octodns/provider/azuredns.py", line 386, in populate
    _records.add(azrecord)
TypeError: unhashable type: 'RecordSet'

I haven't dug around to see if there are other objects in msrest that need similar updates.

The actual hashing logic seems reasonable to me, but I'd welcome suggested improvements.

[codecov-io]

Codecov Report

Merging #182 into master will decrease coverage by 0.02%. The diff coverage is 50%.

@@            Coverage Diff             @@
##           master     #182      +/-   ##
==========================================
- Coverage   87.89%   87.86%   -0.03%     
==========================================
  Files          25       25              
  Lines        2593     2595       +2     
==========================================
+ Hits         2279     2280       +1     
- Misses        314      315       +1

Impacted Files	Coverage Δ
msrest/serialization.py	91.03% <50%> (-0.09%)	:arrow_down:

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[ross]

https://github.com/github/octodns/pull/384 added py3 support

[ross]

Nm. Closed one too many tabs worth. This still applies.

[lmazuel]

As this project is now deprecated, closing.