...so the functions operating on them can all just return osl_File_E_INVAL. (The
way to create an oslVolumeDeviceHandle is via osl_getVolumeInformation storing
it into oslVolumeInfo.pDeviceHandle.  But the unx implementation of
osl_getVolumeInformation never sets that, so it'll stay at the null value that
callers must initialize it to.)

Change-Id: Ibabd89e8f9de0892a0e815d30b6397f869e7df70