Support stopping an allocation

[jrnk]

I noticed stopping an allocation was not yet supported. Hereby.
Thanks for your work!

[codecov-io]

Codecov Report

Merging #111 into master will decrease coverage by 0.04%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #111      +/-   ##
==========================================
- Coverage   78.89%   78.85%   -0.05%     
==========================================
  Files          26       26              
  Lines        1199     1201       +2     
==========================================
+ Hits          946      947       +1     
- Misses        253      254       +1     

Impacted Files	Coverage Δ
nomad/api/allocation.py	96.66% <50.00%> (-3.34%)	⬇️

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[erhlee-bird]

I downloaded your branch and confirmed that the surface functionality is as I expect.

# Create example.nomad and get the full allocation id.
nomad init
nomad run example.nomad
nomad status -verbose example

import sys

import nomad


client = nomad.Nomad()
print(client.allocation.stop_allocation(sys.argv[1]))

{'EvalID': 'ce40dd1e-f002-552e-2844-1fe15617e077', 'Index': 17}

$ nomad status
Allocations
ID        Node ID   Task Group  Version  Desired  Status    Created  Modified
6024fc3b  a7dae536  cache       0        run      running   10s ago  9s ago
556b560e  a7dae536  cache       0        stop     complete  41s ago  10s ago

I additionally ran the tests locally and aside from a few potentially flaky tests, things look good.
Thank you so much for your contribution!

[erhlee-bird]

Looks good, I made one comment on a stylistic change in the tests file that I think would better fit the existing code.

[erhlee-bird]

Looks great, thank you so much for your contribution.