backport PR 383: change the backend role filtering to keep consistent…

[ylwu-amzn]

… with alerting plugin

Issue #, if available:

Description of changes:
backport PR #383

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[codecov]

Codecov Report

Merging #392 (039dde7) into opendistro-1.11 (c4ce051) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@                  Coverage Diff                  @@
##             opendistro-1.11     #392      +/-   ##
=====================================================
+ Coverage              73.10%   73.13%   +0.03%     
  Complexity              2029     2029              
=====================================================
  Files                    201      201              
  Lines                   9599     9590       -9     
  Branches                 853      852       -1     
=====================================================
- Hits                    7017     7014       -3     
+ Misses                  2170     2164       -6     
  Partials                 412      412              

Flag	Coverage Δ	Complexity Δ
cli	79.27% <ø> (ø)	0.00 <ø> (ø)
plugin	72.64% <100.00%> (+0.03%)	0.00 <3.00> (ø)

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Impacted Files	Coverage Δ	Complexity Δ
...opendistroforelasticsearch/ad/util/ParseUtils.java	62.17% <100.00%> (-2.07%)	30.00 <3.00> (-1.00)
...pendistroforelasticsearch/ad/cluster/HashRing.java	78.94% <0.00%> (-5.27%)	10.00% <0.00%> (-1.00%)
...asticsearch/ad/cluster/ADClusterEventListener.java	92.00% <0.00%> (+2.00%)	14.00% <0.00%> (ø%)
...ransport/DeleteAnomalyDetectorTransportAction.java	60.00% <0.00%> (+3.33%)	17.00% <0.00%> (+1.00%)
...port/SearchAnomalyDetectorInfoTransportAction.java	63.63% <0.00%> (+9.09%)	4.00% <0.00%> (ø%)