Support yangson > 1.3.45

[dgjustice]

yangson 1.3.47 breaks two tests

tests/integration/test_integration.py::Test::test_parser[junos_openconfig-vlans] FAILED
tests/integration/test_integration.py::Test::test_parser[ios_test_case_2] FAILED

Both errors are of the type

yangson.exceptions.SchemaError: [$path] config member-not-allowed: $path

[FragmentedPacket]

Just an FYI, I looked into this, and if we pass validate=False to the process() action within these tests, they pass. Still looking into root cause, but I have a feeling it is the way it's constructing and validating these against the YANG models that is causing this to fail.

[FragmentedPacket]

Submitted issue over at Yangson