mix: Make use of pa_cvolume_is_norm/muted() macros

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
log: Cleanup

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
core: Replace assert()s with pa_assert()s

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>