Refine the DSU SD card support

This is part of the work to refine the DSU SD card support. This CL
replaces the StorageVolume with the VolumeInfo to make sure the
installation path starts with a prefix expected by gsid.

Bug: 171861574
Test: execute following command on a device with a SD card inserted
   adb shell am start-activity \
    -n com.android.dynsystem/com.android.dynsystem.VerificationActivity \
    -a android.os.image.action.START_INSTALL \
    -d file:///storage/emulated/0/Download/system.raw.gz \
    --el KEY_SYSTEM_SIZE $(du -b system.raw|cut -f1) \
    --el KEY_USERDATA_SIZE 4294967296

Change-Id: I36083d755c77c755a630f9070d75c14c85282866