Fix for e2e tests

[ChaamC]

Fixes some bugs found while implementing the e2e test that checks Cowbird and Jupyter usage on birdhouse (see PRs #131 and #404):

• The FileSystem handler now creates the WPS outputs data folder if it doesn't exist so that monitoring is setup
  properly.
• User permissions are set explicitly after creating his datastore folder to make sure the user can create and modify
  files in it.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (4a5e77d) 87.57% compared to head (2fe10b3) 87.71%.
Report is 2 commits behind head on master.

Files	Patch %	Lines
cowbird/handlers/impl/geoserver.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #47      +/-   ##
==========================================
+ Coverage   87.57%   87.71%   +0.14%     
==========================================
  Files          40       40              
  Lines        3211     3216       +5     
  Branches      471      471              
==========================================
+ Hits         2812     2821       +9     
+ Misses        278      276       -2     
+ Partials      121      119       -2     

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[ChaamC]

@fmigneault Fixed some check and test errors, need reapproval before I can merge.