Fixed self targeting no parent bug

[TheBurchLog]

If a SystemClient was triggered within a Plugin, without a parent request, it would fail. Instead, do not process this request locally. and let Beer Garden manage it.

[codecov]

Codecov Report

Attention: 155 lines in your changes are missing coverage. Please review.

Comparison is base (95d48b6) 92.39% compared to head (2ac309c) 15.29%.
Report is 19 commits behind head on develop.

Files	Patch %	Lines
brewtils/request_handling.py	3.57%	54 Missing ⚠️
brewtils/pika.py	0.00%	20 Missing ⚠️
brewtils/decorators.py	11.11%	16 Missing ⚠️
brewtils/rest/system_client.py	0.00%	16 Missing ⚠️
brewtils/plugin.py	8.33%	11 Missing ⚠️
brewtils/models.py	20.00%	8 Missing ⚠️
brewtils/rest/client.py	0.00%	7 Missing ⚠️
brewtils/rest/easy_client.py	0.00%	7 Missing ⚠️
brewtils/rest/publish_client.py	0.00%	6 Missing ⚠️
brewtils/auto_decorator.py	16.66%	5 Missing ⚠️
... and 2 more

Additional details and impacted files

@@             Coverage Diff              @@
##           develop     #442       +/-   ##
============================================
- Coverage    92.39%   15.29%   -77.11%     
============================================
  Files           28       28               
  Lines         3644     3766      +122     
============================================
- Hits          3367      576     -2791     
- Misses         277     3190     +2913     

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