THRIFT-2578 Moving 'make cross' from test.sh to test.py

Added "exit" feature to tests.json.
Py server, py client and cpp server "exit" is "hard" while others are "soft".
py server - py client and cpp server - py client are the only combination which has all tests running success.
cpp server - cpp server fails when using domain socket.
Is it okay to get only 'py/gen-py' from tests.json and append '--genpydir=' from script?