Fix Flicker for ZenCustomRuleSettingsBase

Fix the following flicker on pages under:
Notifications -> Do Not Disturb -> Schedules -> [One Schedule]

1. Do Not Disturb behavior
2. (1) -> Create custom settings for this schedule
3. (2) -> Calls
4. (2) -> Messages
5. (2) -> Display options for hidden notifications
6. (4) -> custom

Fix: 226523115
Test: On Pixel Phone
Change-Id: Ief9963091847d58654f26851616563ae910716a5