LockPatternUtils is what drives the TrustAgentsPreferenceController, and therefore should be used to determine how many active trust agents there are. TrustAgentManager filters on whether preferences are displayable in the advanced settings app, which does not represent if the agent is actually active. Test: make RunSettingsRoboTests Bug: 217217034 Change-Id: I8cae74d322b8e0658aabfe7d4646e9a299af4934