Jetpack: Photon: Prevent avatars from loading from Photon on avatar change

Currently when changing an avatar the photo is sent to Photon before the image cropping
step. This causes cropping to fail. This commit disables Photon before cropping the image.
See https://github.com/Automattic/jetpack/pull/57
Merge pull request #122 from Automattic/photon-bp

Jetpack: Photon: Prevent avatars from loading from Photon on avatar chan...