Steps to reproduce:
1. Open attached project
2. Open "first" scene
3. Enter the playmoode
4. Load scenes additively with keys A, S and J
5. Turn off Unity while it is in playmode
6. Open the same project again
7. Notice that additively loaded scenes stays in the hierarchy

Expected behavior:
On relaunch in the scene that was opened before playmode would be no additively loaded scenes

Actual behavior:
Additively added scenes during the playmode stays in the hierarchy

Reproducible with:
5.3.4f1, 5.4.0b14, 5.4.0b15

Workaround:
Reopen the scene