Apply correct SELinux labels to PDX endpoint and channel sockets.

Bug: 37646189
Test: Compiled for sailfish-eng
      Device booted, normal 2D UI works as before
      Was able to run Daydream app and CubeSea (before O1 VR rendering
      path was disabled by recent change in HW composer).

Change-Id: I1f7040324992d3c784f072ea6b64a65fa7ed0589