fix: disk export path to handle dir deletes

[nreisch]

What this PR does / why we need it:
The parent directory needs to be writeable for removing child dirs, so when we mount the writable empty dir, do so at the
tmp/violations, but in the connection path use a child directory ie /tmp/violations/topics

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):
Fixes #4012

Special notes for your reviewer:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 39.12%. Comparing base (3350319) to head (78e14ab).
Report is 393 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (3350319) and HEAD (78e14ab). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (3350319)	HEAD (78e14ab)
unittests	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4021       +/-   ##
===========================================
- Coverage   54.49%   39.12%   -15.38%     
===========================================
  Files         134      243      +109     
  Lines       12329    20515     +8186     
===========================================
+ Hits         6719     8027     +1308     
- Misses       5116    11906     +6790     
- Partials      494      582       +88     

Flag	Coverage Δ
unittests	39.12% <ø> (-15.38%)	⬇️

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[JaydipGabani]

lgtm