Add Inabox backend to proxy e2e tests

[iquidus]

Closes DAINT-798

Adds inabox as a back for proxy e2e tests

TODO

fix setup to properly handle currently failing tests (they should not be failing)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 39.31%. Comparing base (1627f74) to head (72f1b96).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2450   +/-   ##
=======================================
  Coverage   39.30%   39.31%           
=======================================
  Files         552      552           
  Lines       50988    50988           
=======================================
+ Hits        20043    20045    +2     
+ Misses      28413    28412    -1     
+ Partials     2532     2531    -1     

Flag	Coverage Δ
litt-tests	32.99% <ø> (ø)
unit-tests	40.14% <ø> (+<0.01%)	⬆️

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