fs_mgr: allow FDE options in recovery mode

Unfortunately, some recovery fstabs still specify the FDE options, where
they never really did anything anyway.  Allow them for now, since it
seems preferable to restrict any breakage to the case that really
matters (devices actually configured to use FDE in their main fstab).

Bug: 191796797
Bug: 206025578
Change-Id: I85e35af8f42d2aef91f08816a67a71bbf756b211