The autostart value of the apps is not being restored after a restart

[Senyoret1]

Describe the bug
If the autostart value of an application is changed by calling the PUT /api/visors/{pk}/apps/{app} API endpoint, the new value is not restored after stopping the visor and starting it again.

Environment information:

• OS: Linux (Ubuntu 18.04.1)
• Platform: Linux 4.15.0-65-generic x86_64

Steps to Reproduce
Steps to reproduce the behavior:

1. Start some nodes using the make integration-run-generic command of the skywire-services repository
2. Call GET /api/nodes/024ec47420176680816e0406250e7156465e4531f5b26057c9f6297bb0303558c7. The autostart property of the skychat will be true
3. Call PUT /api/nodes/024ec47420176680816e0406250e7156465e4531f5b26057c9f6297bb0303558c7/apps/skychat with {autostart: false} as content, to stop the skychat app.
4. Call GET /api/nodes/024ec47420176680816e0406250e7156465e4531f5b26057c9f6297bb0303558c7 again. The autostart property of the skychat will be false
5. Call make integration-teardown; tmux kill-server in the command window that is running the skywire-services test enviroment, to stop it. Then call make integration-run-generic to start it again.
6. Call GET /api/nodes/024ec47420176680816e0406250e7156465e4531f5b26057c9f6297bb0303558c7 again. The autostart property of the skychat will be true.

Actual behavior
After restarting the visor, the value set by calling PUT /api/nodes/024ec47420176680816e0406250e7156465e4531f5b26057c9f6297bb0303558c7/apps/skychat is ignored.

Expected behavior
The value should survive the restart of the visor.

Additional context

Possible implementation