sink-input, source-output: Fix mute saving
"i->save_muted = i->save_muted || mute" makes no sense. The intention
was most likely to use "save" instead of "mute" in the assignment.
This line originates from reverting the volume ramping code, commit
8401572fd534f10e07ed6a418e1399b1294d5596.
The idea of "i->save_muted |= save" is that even if the mute state
doesn't change, save_muted should still be updated, but only if the
transition is from "don't save" to "save".
Changing "!i->muted == !mute" to "mute == i->muted" is cosmetic only.
The rationale behind the old form was probably that when we still had
pa_bool_t, booleans could in theory be defined as int, so comparing
the values without the ! operator was not entirely safe. That's
unnecessary now that we use the standard bool type, which can only
have values 0 or 1.