sink, source: Allow calling set_mute() during initialization

sink, source: Allow calling set_mute() during initialization

Currently the alsa sink and source write directly to s->muted during
initialization, but I think it's better to avoid direct writes, and
use the set_mute() function instead, because that makes it easier to
figure out where s->muted is modified. This patch prevents the
set_mute() call from crashing in the state assertion.

Change-Id: I12220fb2668723931bebbe1484f115016f1edf25
Signed-off-by: Jaska Uimonen <jaska.uimonen@intel.com>Signed-off-by: Jaska Uimonen <jaska.uimonen@intel.com>