Jetpack: Photon: Only add jetpack_photon_url to the jetpack_photon_url filter if Photon is active!  Let's respect the user's choice with the filter if they choose to deactivate it. Props @frumph


git-svn-id: https://plugins.svn.wordpress.org/jetpack/trunk@754628 b8457f37-d9ea-0310-8a92-e5e31aec5664