There is a wrong format 'ephemeral' in the description.
So remove it and valid formats ('ext2', 'ext3', 'ext4' and 'xfs')
are added.
The parameter is optional, so fix it as well.
Change-Id: Icc04cac3a287955ab1a98b7813e3c7ec8183b120
Closes-Bug: #1736502