[Date Picker] Custom date behavior is not consistent

[graceguo-supercat]

Screenshots

Expected Behavior

• Find the right user input.
• CUSTOM start/end date should always automatic updated when user set DEFAULTS or relative section
  (this is old behavior before recent changes)

Environment

latest master

Checklist

Make sure to follow these steps before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven't found one similar.

Additional context

Add any other context about the problem here.

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[junlincc]

we noticed this issue as well but have not been able to reproduce it consistently. will looking into it!