Merge pull request #3949 from ThomasWaldmann/use-pyi-331

vagrant: use pyinstaller v3.3.1

Vagrantfile

@@ -143,7 +143,7 @@ def install_pyinstaller()
     . borg-env/bin/activate
     git clone https://github.com/thomaswaldmann/pyinstaller.git
     cd pyinstaller
-    git checkout v3.3-fixed
+    git checkout v3.3.1
     python setup.py install
   EOF
 end