CMUpdater: only list updates for current channel

Steam crossing is bad. CMUpdater should not offer to install M
snapshots over nightlies, and vice versa. Offer only updates that
correspond to the currently installed cm.releasetype. M snapshots only
display newer updates, while nightlies display all available nightlies.

Change-Id: I3b9f445d61815dbec9db9477d460d1b74458bc95
Automatic translation import

Change-Id: I762b99c0190414ff587a86985a8ac7afbf505c98
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_packages_apps_CMUpdater.git into 'cm-11.0'