VistATestClient: Add telnet host/port as input parameters

Also set the default values for telnet host and port.
Change waitForPrompt method timeout value to the default one.
Add two test functions in VistATestClient and create a
Python Unit Test script for it.

OSEHRA-Id: http://issues.osehra.org/browse/OAT-130
Change-Id: I3d7c780afab8623ec518c6e9c92b5e1dc1ee4663
Merge "VistATestClient: Add telnet host/port as input parameters"