Problem was twofold
1) `GENERATOR_IS_MULTI_CONFIG` is a property not a variable so
the test for it would always be false, unless you set a custom
CMAKE_INSTALL_PREFIX (like the buildbot does) the unit tests
would have a wrong working directory and complain about missing
dlls or blender executable
2) Tests added outside of `/test` (like libmv) would have no working
folder set since the variable would not be visible for them.
consulted @sergey who voiced the opinion that duplicating the code
to the test macro was slightly less evil than moving it to the main
CMakeLists.txt
Simply disabled python tests, they can't be run anyway (since blender target is
not enabled) and we don't have any player-related tests in that folder.
