getVolumeUUID: add workaround to fetch FUSE-mapped sdcard UUID

Allows the mediaserver to recovery properly after a crash of the
system_server thread. This is needed for a specific storage
configuration (non-emulated physical primary only).

Note: this is an ugly hack, replacing /dev/fuse with
      /dev/block/mmcblk0p1.

Change-Id: I337bda5dfcf70f85a5ad50d03ffdc3de9b4ba06b