vboxwrapper: don't create projects/virtualbox

[davidpanderson]

If Vboxwrapper couldn't find the Vbox 'home dir' (normally ~/.VirtualBox) based on env vars, it would create one: projects/virtualbox (owned by boinc_projects, not boinc_master)

This is wrong because

1. on startup, the client deletes anything in projects/ that's not a project directory
2. on Mac it causes installer error messages because the dir is not owned by boinc_master.

Fix: don't create projects/virtualbox.

[AenBleidd]

@computezrmle, could you please review this change?

[computezrmle]

The docs mention different directories to put VirtualBox.xml in depending on the host OS:

Linux and Oracle Solaris:$HOME/.config/VirtualBox.
Windows:$HOME/.VirtualBox.
macOS:$HOME/Library/VirtualBox.

It looks like the patch covers the situation on Windows only.

On Linux and Oracle Solaris XDG_CONFIG_HOME can be used instead of VBOX_USER_HOME. This case may also be implemented.

[davidpanderson]

Other than the comment, is the change OK?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 10.53%. Comparing base (505b841) to head (0883a68). Report is 46 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5658      +/-   ##
============================================
- Coverage     10.53%   10.53%   -0.01%     
  Complexity     1068     1068              
============================================
  Files           279      279              
  Lines         35868    35874       +6     
  Branches       8409     8412       +3     
============================================
  Hits           3780     3780              
- Misses        31694    31700       +6     
  Partials        394      394              

see 3 files with indirect coverage changes