Set the log callback earlier for showing system property set denials

PropertyInit loads the build.prop files and set the system properties.
Set the SELinux log callback before that to show the avc denials for debugging.

Test: $ make init_system
      Push this module and ensure system property set denials are shown during boot
Bug: 185920634
Change-Id: Ifc228985a990f6938ad2a93790eb3607b2d12b5a