Updating to 4.2.1
Temporarily disable REST for Jetpack sites

It just doesn't work when the JSON API module is disabled.
Also, there are some issues where failed uploads don't show any error.
Merge pull request #2279 from wordpress-mobile/issue/2258-rest-jetpack-fail

Temporarily disable REST for Jetpack sites
Merge branch 'release/4.2.2' into release/4.3

Conflicts:
	WordPress/Info.plist
Merge branch 'release/4.3' of github.com:wordpress-mobile/WordPress-iOS into release/4.3