Add a rpc utility library for commonly used functions

[harendra-kumar]

For example add APIs for:

• installing the rpc executable at a well-known location
• Checking for ssh access to machines

The rpc executable can be installed in user $HOME/.rpc directory. That way any user can use it without requiring sudo access.

We can supply an rpcAccessCheck API to check that we have ssh access setup properly for the list of machines/users supplied before we start executing. That way we reduce the chances of failure halfway through the script, after mutating some state which cannot be rolled back.