audio: fix offload enabling test parameter

passing NULL as the default to property_get doesn't return false,
it returns random memory junk that evaluates to true... Explicitly
default the state of this property to "false" as a default

Change-Id: Ib2808bf2540b2b4fdf754d489fb44aa5d9e061a8
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_hardware_libhardware_legacy into cm-11.0