switch off console appenders when running as backend services

[nobodyiam]

What's the purpose of this PR

switch off console appenders when running as backend services

Which issue(s) this PR fixes:

Fixes #3272 #2459

Brief changelog

1. add LOG_APPENDERS environment variables to make logback appenders switchable
2. set LOG_APPENDERS=FILE when running as backend services
3. upgrade spring-boot-maven-plugin to 2.0.5.RELEASE

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• Read the Contributing Guide before making this pull request.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit tests to verify the code.
• Run mvn clean test to make sure this pull request doesn't break anything.

[codecov-io]

Codecov Report

Merging #3488 (dd118f3) into master (41519f4) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #3488   +/-   ##
=========================================
  Coverage     51.44%   51.44%           
+ Complexity     2320     2319    -1     
=========================================
  Files           442      442           
  Lines         13843    13843           
  Branches       1408     1408           
=========================================
  Hits           7121     7121           
  Misses         6230     6230           
  Partials        492      492           

Impacted Files	Coverage Δ	Complexity Δ
...mework/apollo/openapi/service/ConsumerService.java	47.57% <0.00%> (-1.95%)	12.00% <0.00%> (-1.00%)
...amework/apollo/openapi/util/ConsumerAuditUtil.java	91.89% <0.00%> (+5.40%)	8.00% <0.00%> (ø%)

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