The setban() RPC was returning misleading or incorrect error
codes (for example RPC_CLIENT_NODE_ALREADY_ADDED when an invalid IP
address was entered). This commit fixes those error codes:
- RPC_CLIENT_INVALID_IP_OR_SUBNET should be returned if the client
enters an invalid IP address or subnet.
This commit also updates the test cases to explicitly test the error code.
This commit also adds a testcase for trying to setban on an invalid subnet.
This commit fixes the module-level docstrings for the tests and helper
modules in qa. Many of these tests were uncommented previously - this
commit ensures that every test case has at least a minimum level of
commenting.
