Improve isolation of DND providers

Specifically, a change in state from one DND provider
shouldn't result in another's state being cleared if they
aren't yet bound (or are intentionally unbound).

Fixes: 111251709
Test: cts, cts-verifier

Change-Id: I42a0ba935577e708d9df02e2a6d3620e42395a51
(cherry picked from commit 8f056001)