Collect fan status information for EX series switches

[tomhughes]

This collects fan status information for EX series switches which don't report speeds but do report a basic status with a response like:

<environment-item>
    <name>FPC 0 Fan 0</name>
    <class>Fans</class>
    <status>OK</status>
    <comment>Spinning at normal speed</comment>
</environment-item>

as well as an airflow status for each fan:

<environment-item>
    <name>FPC 0 Fan 0 Airflow</name>
    <class>Fans</class>
    <status>OK</status>
    <comment>Airflow Out (AFO)</comment>
</environment-item>

[czerwonk]

LGTM

[czerwonk]

Thanks for your contribution! :)