Use StartFuseBridgeLoop function instead of FuseBridgeLoop class.

The method is being renamed from FuseBridgeLoop::Start to StartFuseBridgeLoop
in libappfuse. The CL handles the change in the framework side.

Bug: 29970149
Test: None
Change-Id: I70b91e426fa817d84c7f1f5f24c9e3ba401e523b