Conditionally use sdcardfs.

In preparation of sdcardfs going away on devices launching with R,
conditionally use it.

Bug: 146419093
Test: cuttlefish with sdcardfs, cuttlefish without sdcardfs but with
FUSE
Change-Id: I2c1d4b428dcb43c3fd274dde84d5088984161993
5 files changed