The "doh-rollout.self-enabled" pref is not removed after disabling DNS from “about:preferences” page and reconnecting to the network twice

[SoftVision-CarmenFat]

[Affected Platforms]:

• All Windows

[Affected Versions]:

• Firefox Release 70.0.1, Build ID 20191030021342

[Prerequisites]:

• Have an active Normandy testing recipe for DoH.
• You are enrolled in the Treatment branch.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Navigate to "about:preferences#networking" page.
3. Click the "Settings" button and uncheck the "Enable DNS over HTTPS" checkbox.
4. Click the "OK" button.
5. Disconnect and reconnect to the network twice.
6. Wait for 60 seconds and navigate to "about:config".
7. Verify that the "doh-rollout.self-enabled" is removed.

[Expected result]:

• The "doh-rollout.self-enabled" pref is removed.

[Actual result]:

• The "doh-rollout.self-enabled" pref remains set as "true".

[Notes]:

• The "doh-rollout.self-enabled" pref is not removed even after you restart the browser after performing the steps above.
• This issue is not reproducible when restarting the browser twice instead of network reconnection.
• I have made a screen recording of the issue: https://tinyurl.com/vbnm96g.