Turn off transcoding notification by default

To aid debugging, we included transcoding progress
notifications. We don't intend to launch with the notifications on by
default so turn it off now in preparation for Android S launch.

The notifications can still be enabled in the developer options with:
Settings > System > Developer options > Media transcoding >
Show transcoding notifications

Icab62cb91fdf22e5308d0c4bbc710b88a51170d3 attempted turning this off
but only turned off the default value in the Settings check-box

Test: Manual
Bug: 194911314
Change-Id: I23dceae40b01f4d6277d80af17a3753768825ad3
1 file changed