Refactoring and clean-up of duplicate code

[WadeBarnes]

The circular dependances described in #102 have been addressed by #109.

The PR addressed the issues by creating a new ./system_node_only folder which does not contain any of the Sovrin dependencies. In the process much of the code was duplicated. In the interest of time this was deemed acceptable. This ticket is the placeholder for the refactoring and cleanup activities that would need to follow to address the duplicate code.

The similarities and differences between the ./system and ./system_node_only tests are described here; https://github.com/hyperledger/indy-test-automation/tree/main/system_node_only#similarities-between-system-and-system_node_only

Some thoughts on the direction the refactoring and cleanup could go can be found in the Next Steps (as I see them) section of this comment; #102 (comment)