ubuntu_lxc api_test.py fails when lo interface exists

[Portia Stephens]

api_test.py from python3-lxc fails when there is a lo ethernet interface. This issue is fixed upstream.

https://github.com/lxc/python3-lxc/commit/69c41ef51363539226fa362be6f459d39ff1e2cc

This causes the ubuntu_lxc kernel test case to fail when CONFIG_IPV6_SIT is enabled. The failure looks this this:

ERROR| [stderr] Traceback (most recent call last):
ERROR| [stderr] File "/usr/share/doc/python3-lxc/examples/api_test.py", line 109, in~
ERROR| [stderr] assert(set(container.get_interfaces()) == set(('lo', 'eth0')))
ERROR| [stderr] AssertionError
ERROR| Exception escaping from test:
Traceback (most recent call last):
  File "/home/ubuntu/autotest/client/shared/test.py", line 411, in _exec
    _call_test_function(self.execute, *p_args, **p_dargs)
  File "/home/ubuntu/autotest/client/shared/test.py", line 823, in _call_test_function
    return func(*args, **dargs)
  File "/home/ubuntu/autotest/client/shared/test.py", line 291, in execute
    postprocess_profiled_run, args, dargs)
  File "/home/ubuntu/autotest/client/shared/test.py", line 212, in _call_run_once
    self.run_once(*args, **dargs)
  File "/home/ubuntu/autotest/client/tests/ubuntu_lxc/ubuntu_lxc.py", line 100, in run_once
    utils.system_output(cmd, retain_output=True)
  File "/home/ubuntu/autotest/client/shared/utils.py", line 1268, in system_output
    verbose=verbose, args=args).stdout
  File "/home/ubuntu/autotest/client/shared/utils.py", line 918, in run
    "Command returned non-zero exit status")
CmdError: Command failed, rc=1, Command returned non-zero exit status
* Command:~
    python3 /usr/share/doc/python3-lxc/examples/api_test.py
Exit status: 1