move the mock_open util to fakes

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
fix invalid path handling

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
add mock imports to fakes

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
return the path for the home config

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
create tests for the new conf utils

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>