Don't query active mode after setting desired mode specs

We don't need to query the active display mode after
setting desired mode specs. If the mode changes
the onModeChanged() will be called and we'll update
the state.

Bug: 180090041
Test: presubmit
Test: flashed on device and did a mode switch
Test: atest DisplayTest
Change-Id: Ie77e1caf29fecfc4e43d6d3b6ec73c9bfdfc8a5c