Load mu-plugins for O2 only when O2 is active

[ocean90]

On ​https://wordpress.org/news/ or ​https://developer.wordpress.org/ the inline terms plugin is loaded:

<link rel='stylesheet' id='jetpack-inline-terms-css-css'  href='https://developer.wordpress.org/wp-content/mu-plugins/inline-terms/ui/style.css?ver=4.7-alpha-38257' type='text/css' media='all' />
<script type='text/javascript' src='https://developer.wordpress.org/wp-content/mu-plugins/inline-terms/ui/atwho.min.js?ver=4.7-alpha-38257'></script>
<script type='text/javascript' src='https://developer.wordpress.org/wp-content/mu-plugins/inline-terms/ui/defaults.min.js?ver=4.7-alpha-38257'></script>
<script type='text/javascript' src='https://developer.wordpress.org/wp-content/mu-plugins/inline-terms/ui/xposts.min.js?ver=4.7-alpha-38257'></script>
<script type='text/javascript' src='https://developer.wordpress.org/wp-content/mu-plugins/inline-terms/ui/hashtags.min.js?ver=4.7-alpha-38257'></script>

[Otto42]

Note that disabling this in the most obvious way results in breakage in wporg-o2-compat.php. Specifically in the enqueue_inline_terms_ui() function, which probably needs to check for existence of the class before calling it.

[pento]

Fixed in [dotorg12347].