veyron/lib/modules: adding an option to pass Config to a child process
veyron/lib/modules: adding an option to pass Config to a child process

This CL extends the modules package with the ability to pass a
configuration to the processes spawned by the veyron exec library.

This mechanism is then used to replace the hardcoded server address in
the management runtime component, with values specified in the
configuration.

Change-Id: I3df226d1550bb9194bf240943683313f603f6600

vanadium/go.v23,vanadium/go.v23,vanadium/go.v23