Jetpack: Monitor: Only allow the master user to [de]activate Monitor

Previously, any user with access to change options could activate or
deactivate Monitor, but now only the user who initiated the connection
with WordPress.com is permitted to alter Monitor because that is the
user who will receive any emails sent by it.


git-svn-id: https://plugins.svn.wordpress.org/jetpack/trunk@807032 b8457f37-d9ea-0310-8a92-e5e31aec5664