cli:apply: initialize self.state (LP: #1949104)

[slyon]

Description

The self.state attribute needs to be available even if NetplanApply() is not executed via the command line (and thus the run() method is not executed).

Fixes a regression in #231

Checklist

• Runs make check successfully.
• Retains 100% code coverage (make check-coverage).
• New/changed keys in YAML format are documented.
• (Optional) Adds example YAML for new feature.
• (Optional) Closes an open bug in Launchpad: LP#1949104

[schopin-pro]

LGTM, but it'd be even nicer with a test that triggers the fixed bug :)

[slyon]

I agree. netplan try modifies the running system, so we cannot easily wrap this into an unit test. But I've created two new integration tests that execute netplan try and accept and reject the configuration accordingly, checking for the correct output.