Fixed downloading incremental updates.

onResponse() received the UpdateInfo for the incremental but it was
never used.

Change-Id: Ia699bbf5ac133f69c4820286d844ab1bb678887d
Rename two variables to make it clear what's stored inside them.

Change-Id: Idab69ebc94a5e8ff9ad9a971ddd0804ca89b4574
Small code-cleanup.

This removes an unused method and cleans up duplicate code.

Change-Id: Ic3be1cf49b391c6bfc89b59535802e633666fecb