FakeDeviceProvisionedController: allow un-setting-up user

In VisualInterruptionDecisionProviderTestBase, I'm using a single
FakeDeviceProvisionedController with a single user ID across multiple
test cases, and I need to be able to change what isCurrentUserSetup on a
per-case basis.

Therefore, add an "isSetup" parameter to setUserSetup that lets callers
un-set-up a user.

Also, add a convenience method to 'set' isCurrentUserSetup directly.

Bug: 326356165
Flag: NA
Test: NA
Change-Id: I8dbe09cacb6bfc8ea4e2ad66924deece22930a6e