Fix problem where rotating the device doesn't launch TrustAgent pref

This fixes a bug where the TrustAgent intent was being lost when
the device configurtion changes. It used to depend on a view that
gets recreated.  Instead, we persist the actual launch intent
which works across activity restarts.

Fixes bug 17040470

Change-Id: Ia1c93867254cfdc27683a767cf41fe74dbb97db0