Added firefox profile option to acceptance tests with selenium and behat

[skjnldsv]

@danxuliu

[codecov]

Codecov Report

Merging #9438 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #9438      +/-   ##
============================================
+ Coverage     51.61%   51.61%   +<.01%     
+ Complexity    25694    25684      -10     
============================================
  Files          1638     1638              
  Lines         96315    96283      -32     
  Branches       1393     1393              
============================================
- Hits          49713    49697      -16     
+ Misses        46602    46586      -16

Impacted Files	Coverage Δ	Complexity Δ
lib/private/Files/Cache/Propagator.php	94.93% <0%> (-1.27%)	16% <0%> (ø)
apps/files_trashbin/lib/Trashbin.php	72.7% <0%> (+0.24%)	136% <0%> (ø)	⬇️
lib/private/legacy/api.php	35.41% <0%> (+1.04%)	31% <0%> (ø)	⬇️
lib/private/AppFramework/OCS/BaseResponse.php	80.76% <0%> (+4.9%)	4% <0%> (-10%)	⬇️
lib/private/legacy/json.php	12% <0%> (+12%)	19% <0%> (ø)	⬇️

[danxuliu]

Overriden by #9521

I created a different pull request instead of amending this one to leave it as future reference, just in case this technique is needed later. In any case note that currently this technique works only for acceptance tests run in local, but not for those run in Drone.