SF: Query display modes only once during display creation / update

Currently HWComposer::getActiveMode / getModes is called multiple
times when creating or updating a display. This is unnecessary
and risky because the getActiveMode may return a different value
if a hotplug event has ocured in between.

In this CL we call getActiveMode and getModes only once and propagate
the values using DisplayDeviceState.

Bug: 159590486
Test: presubmit
Change-Id: I97418163426a0ae19f79bc2912a7d725c953ad01