Remove obsolete permission checking.

This dead  code doesn't handle coexistence, instead treats all permission-
based callers as one admin. This removed code can still be found in the
version control if necessary during proper migration to permission-based
access.

Removing this code makes it easier to improve and refactor the actual
working code.

Bug: 335663055
Test: TH
Flag: EXEMPT 99% mechanical refactoring
Change-Id: I8f983461e1d6c0401f60c93f10c403d42b0b733f