Fix cc_rsyslog.py initialization

[aciba90]

Proposed Commit Message

Fix cc_rsyslog.py initialization

Raises an error if some top level config value has an invalid type.
Previously, it replaced them with default values.

Fixes: SC-878

Test Steps

Execute cloud-init with this config:

#cloud-config
rsyslog:
  config_dir: True

Expected error:

"Invalid type for key `config_filename`. Expected type(s): <class 'str'>. Current type: <class 'bool'>"

Checklist:

• My code follows the process laid out in the documentation
• I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[TheRealFalcon]

LGTM, thanks!