ChoiceField defined with integer option values fails to indicate field state in HTML form output

[arkadini]

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

• in a serializer, have a ChoiceField where choices' option values are integers
• in the HTML form representation:
  • pick a valid choice for the field in question
  • submit

(see #4119 for an exact test case)

Expected behavior

The choice that was selected and submitted should be shown as selected choice in the HTML form field.

Actual behavior

The field in question never shows any currently set value.