Adds support for multi-node run/testing and updates tests

[dbbaughe]

Issue #, if available:

Description of changes:
This adds support in gradle to run and test multinodes.
Updates tests to work in both single/multinode setup.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #254 into master will increase coverage by 0.13%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #254      +/-   ##
============================================
+ Coverage     71.31%   71.44%   +0.13%     
  Complexity      633      633              
============================================
  Files            86       86              
  Lines          3646     3646              
  Branches        603      603              
============================================
+ Hits           2600     2605       +5     
+ Misses          732      729       -3     
+ Partials        314      312       -2     

Impacted Files	Coverage Δ	Complexity Δ
...ticsearch/indexstatemanagement/model/Transition.kt	82.35% <0.00%> (+1.96%)	5.00% <0.00%> (ø%)
...dexstatemanagement/elasticapi/ElasticExtensions.kt	71.42% <0.00%> (+4.08%)	0.00% <0.00%> (ø%)
...ndexstatemanagement/IndexStateManagementIndices.kt	64.58% <0.00%> (+4.16%)	10.00% <0.00%> (ø%)

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