improve nodejs driver for shared data and child process exit

implementing message handshaking between child and parent process.

It is supposed to fix two issue in NodeJS Driver.

First, "Failed to get test result" error even the test result are generated by child process.
- cause: child process exit too soon before parent process can retrieve the test result.
- solution: implementing handshaking for child exit. There is also a 1000 ms exit timeout if child did not receive exit message from parent process.

Second, shared data is limited by the size of process argument list, 128KB.
- cause: argument list size is 128KB in linux system. Right now, we pass shared data thru process argument list to child process.
- solution: implementing handshaking for shared data. There is also a 1000ms timeout if child did not receive shared data. After timeout, child process will proceed testing without shared data.