Support for Proxy Implementations that needs Preemptive authentication

[rb-john]

for issues #201 add the call to setAuthenticationPreemptive(true) to support proxy calls that do not return unauthenticated status.

[codecov]

Codecov Report

Merging #202 into master will decrease coverage by 0.18%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #202      +/-   ##
==========================================
- Coverage   90.34%   90.16%   -0.19%     
==========================================
  Files          19       19              
  Lines         487      488       +1     
  Branches       71       71              
==========================================
  Hits          440      440              
- Misses         39       40       +1     
  Partials        8        8              

Impacted Files	Coverage Δ
...jenkins/plugins/office365connector/HttpWorker.java	50.98% <0.00%> (-1.02%)	⬇️

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[damianszczepanik]

Did you check if this works with your configuration for which you have submitted this change?