This makes NodeConnCB a subclass of NodeConn, and
removes the need for the client code to know
anything about the implementation details of NodeConnCB.
NodeConn can now be swapped out for any other implementation
of a low-level connection without changing client code.
p2p connections can now be added to TestNode instances.
This commit also updates the example test to use the new
p2p interface in TestNode to demonstrate usage.
A future commit will update the existing tests to use p2p through the
TestNode.
Almost all test scripts currently need to override the __init__()
method. When they do that they need to call into super().__init__() as
the base class does some generic initialization.
This commit makes the base class __init__() call into set_test_params()
method. Individual test cases can override set_test_params() to setup
their test parameters.
John Newbery