Disable debinterfaces tests on Windows

[wupeka]

Please provide the following details to expedite Pull Request review:

Disable debinterfaces activation tests on Windows, those are Linux specific.
Fix debinterfaces parsing tests on Windows.

Description of change

Tests were failing on Windows

QA steps

Tests for debinterfaces should pass on Windows.

[wupeka]

!!Test!!

[jameinel]

we have github.com/juju/juju/testing.SkipIfWindowsBug()

I'm not sure if we would ever intend for BridgeSuite to pass on Windows. Parser feels more like something that we should make pass, rather than skip. (we shouldn't be depending on shelling out to a command to parse the file, right?)

So BridgeSuite feels like something we might not ever intend to fix, so creating a bug doesn't feel appropriate. But for ParserSuite, if we aren't fixing it now, then we should have a bug to come back to this.
There's an argument whether it is worth the effort, but IMO, not running go code on Windows is usually a sign of not-very-good-code and is likely to bite us again somewhere, which is generally why I feel Skip() should be reserved for things that really won't run everywhere.

[wupeka]

I don't think SkipIfWindowsBug is appropriate here because it's not a bug, we are skipping some tests this way.
parser_tests are fixed - those should work on Windows without problem now (although I don't have environment to test it)

[babbageclunk]

$$merge$$

[babbageclunk]

Merging because @wupeka asked me to on IRC.

[jujubot]

Status: merge request accepted. Url: http://juju-ci.vapour.ws:8080/job/github-merge-juju