Check silent mode when updating output device.

After refactoring audio device type, the output devices will only be set
when create/release audio patch. In that case, the output devices are
empty when creating the thread. If the "ro.audio.silent" is set, it will
make master muted if the output devices are empty. To fix the issue, do
not check silent mode when the output devices are empty, but check
silent mode when output devices are updated.

Test: atest AudioHostTest with setting "ro.audio.silent"
Bug: 154037767
Change-Id: I6cb219353e541ba99ba9acebd6ce853128d963d3