This shim was required to support Python 2.6, so we no longer need it.

Previously, init.paths.cloud_dir has a trailing slash, which meant that
"/var/lib/cloud//seed" was being compared to "/var/lib/cloud/seed" and
(of course), never matching.

In this commit, switch to using os.path.join to avoid this case (and
update the tests to catch it in future).

LP: #1818571

Avoid traceback when cloud-init clean is run from within
/var/lib/cloud/ deleted dirs.

LP: #1795508

When we moved some tests to live under cloudinit/ we inadvertantly
failed to change all things that would run nose to include that
directory.

This changes all the 'nose' invocations to consistently run with
tests/unittests and cloudinit/.

Also, it works around, more correctly this time, a python2.6-ism with
the following code:
   with assertRaises(SystemExit) as cm:
      sys.exit(2)

Fix cloud-init clean subcommand to unlink symlinks instead of calling
del_dir.

LP: #1741093

The motivation for this is that
 a.) 1.7.1 runs with python 3.6 (bionic)
 b.) we want to run pylint on tests/ and tools for the same reasons
     that we want to run it on cloudinit/

The changes are described below.
- Update tox.ini to invoke pylint v1.7.1.
- Modify .pylintrc generated-members ignore mocked object members (m_.*)
- Replace "dangerous" params defaulting to {}
- Fix up cloud_tests use of platforms
- Cast some instance objects to with dict()
- Handle python2.7 vs 3+ ConfigParser use of readfp (deprecated)
- Update use of assertEqual(<boolean>, value) to assert<Boolean>(value)
- replace depricated assertRegexp -> assertRegex
- Remove useless test-class calls to super class
- Assign class property accessors a result and use it
- Fix missing class member in CepkoResultTests
- Fix Cheetah test import

The 'cloud-init clean' command allows a user or script to clear cloud-init
artifacts from the system so that cloud-init sees the system as
unconfigured upon reboot. Optional parameters can be provided to remove
cloud-init logs and reboot after clean.

The 'cloud-init status' command allows the user or script to check whether
cloud-init has finished all configuration stages and whether errors
occurred. An optional --wait argument will poll on a 0.25 second interval
until cloud-init configuration is complete. The benefit here is scripts
can block on cloud-init completion before performing post-config tasks.