Refine the DSU SD card support

Refine the openImageService and allow images to be installed in a SD card.
This also fixes the error when execute the "gsi_tool status" command.

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: I764cf66984e74ab66cc4316b087751937e20a242
2 files changed