vold: fix failing to format zero-ed out SD card

sgdisk --android-dump fails with error code 8 when there is no partition
table. Don't stop us from creating a new partition table.

Can be reproduced with
1. adb shell sm set-virtual-disk true
2. Format from UI
3. Observe fake "success" message with SD still unformatted

Fixes: ad5b4f9 ("vold: skip first disk change when converting MBR to GPT")
Test: CtsOsTestCases android.os.storage.cts.StorageManagerTest#testGetStorageVolumeSDCard
Change-Id: I3262bb2e28de438beba541a97038a06432643a65
1 file changed