init.te: allow creating kernel audit entries

Allow init to send userspace generated SELinux denials to the kernel
audit subsystem.

Test: "setprop asdf asdf" from the unprivileged adb shell user
      generated an SELinux denial processed by logd.
Bug: 27878170
Change-Id: I0ecd0601408bbda8227802c13689f98e507282d1