Temporarily disable abc-cmdline.py test

Summary:
This test produces some expected stderr output from the application.
The test framework (rpc-tests.py) wrapper considers this a sign of
test failure, even if the test passes successfully when executed
on its own.

We need to teach the test framework about expecting certain output on
stderr. This will take a while however, so this test is temporarily
disabled and needs to be run manually when changing command line
options.

Test Plan: qa/pull-tester/rpc-tests.py

Reviewers: #bitcoin_abc, deadalnix, sickpig, kyuupichan

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D176