Enable metadata encryption for userdata_gsi.

When running a live GSI, userdata is a logical partition. If we don't
fix up the fstab we'll derive the underlying block device instead of
the device-mapper node for userdat_gsi, resulting in a corrupt data
partition for both images.

Bug: 123906417
Test: manual test
Change-Id: Ic0101f30504de26e725442da2da3888008c31b63
1 file changed