Use the common entity type definitions in system_test.py

[ganeshmurthy]

There are many instances in the test code that do not use the common entity types that are already defined in system_test.py.

It would be good to use these common entity types in all system tests so there is one place that holds a record of these entity types (long form).

For example - the following types are already in system_test.py

HTTP_LISTENER_TYPE = 'io.skupper.router.httpListener'
TCP_LISTENER_TYPE = 'io.skupper.router.tcpListener'
HTTP_CONNECTOR_TYPE = 'io.skupper.router.httpConnector'
TCP_CONNECTOR_TYPE = 'io.skupper.router.tcpConnector'
CONNECTION_TYPE = 'io.skupper.router.connection'

Use the above types and add new types to system_test.py wherever necessary