Use a config flag instead of a RO flag for showing Manage Storage.

Bug: 30455784
Test: make SettingsTests; run the instrumentation.
Change-Id: I860192c1c20fcaec2a5cbcdc085ff01dafa7351a
(cherry picked from commit 7f075a3c41f02d58bae10fb3f2b4a4ad8ada8967)
3 files changed