common: Recursively remove our temporary XDG_RUNTIME_DIR

If we create our temporary XDG_RUNTIME_DIR path, we ought to clean it up on termination.

However, there might still be residual files in that path, created by other programs.

So we need to remove the tree recursively, not just the base directory.

Signed-off-by: Olivier Fourdan ofourdan@redhat.com
Closes: #8 (closed)
Fixes: 45232be5 - common: Create and export XDG_RUNTIME_DIR if needed