Disable Dalvik spam by default

Reverse the logic: use "dalvik.vm.debug.alloc=1" to see these lines.

Change-Id: Id58de1dd09467c2327f76d37eeb926b712d6af52
libdex: Skip the dexroot-on-cache stuff for user builds

Change-Id: I432b96ae3e25977ea17558b4a3f8ca90903cb5b5