Not overriding status code for non-core-Servlet Exceptions

[eyalkoren]

What does this PR do?

Fixes the bug of setting a 500 status code on responses from error pages that actually return 200 but with an Exception set as a Request attribute

Checklist

• My code follows the style guidelines of this project
• I have rebased my changes on top of the latest master branch

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

• I have updated CHANGELOG.asciidoc

Related issues

Fixes #1036

Use cases

Using Exception handlers that do not return an error status code

[codecov-io]

Codecov Report

Merging #1103 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1103   +/-   ##
=========================================
  Coverage     60.10%   60.10%           
  Complexity       87       87           
=========================================
  Files           327      327           
  Lines         14828    14828           
  Branches       2087     2087           
=========================================
  Hits           8912     8912           
  Misses         5318     5318           
  Partials        598      598           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 97a3d76...d3248f5. Read the comment docs.