am 867f8b45: unmount cache before paving it over with the radio/hboot image

Merge commit '867f8b454d754ff496b66527407753c451f54277' into gingerbread-plus-aosp

* commit '867f8b454d754ff496b66527407753c451f54277':
  unmount cache before paving it over with the radio/hboot image