Volume release value modification not permanent

Nobody has claimed this yet.

### Bug Summary
Don't know if it's supposed to be the intended way but it doesn't do that in 1.2.2 : Changing the volume release value after a note is released is not a definitive process, and changing it back makes it sound as if nothing was modified. It makes 1.2.2 envelope automation unpractical in 1.3.0

#### Steps to reproduce
- Put the release to 2
- Play a note and release it -> Note is playing
- Put the release to 0 -> Note is not playing
- Put the release back to 2 -> Note is playing

#### Expected behavior
The instrument should modify the envelope of the currently playing sound instead of the original, and thus playing a note with a release value x, releasing it, then setting the release to 0 and then back to x shouldn't produce any sound.

#### Actual behavior
The instrument modifies the envelope of the original note, and thus playing a note with a release value x, releasing it, then setting the release to 0 and then back to x makes the note plays as if its release never changed.

#### Affected LMMS versions
1.3.0-alpha-1.33+g4f74151 to 1.3.0-alpha-1.72+g7aa30c4ec
(Linux/x86_64)

Start by reproducing the release automation sequence in LMMS 1.3.0 using the listed steps, then trace the envelope handling for a released note. Done means changing the release value after note release permanently affects that currently playing sound, including when the value is changed back.

Written by the indexing model from the issue text.