Skip logging the warning for uncrypt_status for devices w/o /cache

This warning may cause confusion for users.

Bug: 36590598
Test: Warning line no longer shows for sailfish.
Change-Id: I277c87a50a72fdb499be790ee25b97f815d980be
(cherry picked from commit bcb5b18630f518835a0768535b43ccfe91683fc9)