RequestNotification/InstanceNotificationFilter filter not saved

[Anthony]

Describe the bug
RequestNotification filter not saved properly for fields services and operations.

Same for InstanceNotification for field services. It seems that it's a bug with m2m fields

To Reproduce
Steps to reproduce the behavior:

1. Create a RquestNotification filter
2. Add services and opreations
3. Save it
4. Edit it
5. Services and operations are not set

Expected behavior
Make it works

• Squest version or GIT commit number: v2.2.0 - d46ce7
• Ansible Tower/AWX version: N/A

[Elias]

+ API does not work anymore, we got 500 error

[Nicolas Marcq]

Done and merged in dev branch