Handling of 'with-defaults' tag incorrect

[psch-k]

Hi,
actually, the test 'test_ietf_interfaces.py' fails. The reason is, that the API to ncclient is different than what is implemented in the test just mentioned; at least, for the actual version of ncclient (version 0.6.6).
I don't know when this 'feature' changed, I assume the handling of this tag in test_ietf_interfaces.py was correct in earlier times.
I appended the necessary 'git diff'.
(Additionally, the 'git diff' contains a small change in 'nctest.py', to make it python3 compatible.)
Just to let you know. It may help if you run into trouble with this test.
sn2s_ncclient_0.6.6.patch.txt