Add missing preconditions to get/setDefaultApplicationAsUser

Add missing preconditions to ensure these methods are not called on APIs
lower than U

Bug: 379362792
Flag: EXEMPT bug fix
Relnote: Fix API preconditions
Test: atest RoleManagerSecurityTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:f21634af468653cce28dfd329998f0eaa85608d4)
Merged-In: Iadc97d09cf083e2525de421362c5a4bece92ee8a
Change-Id: Iadc97d09cf083e2525de421362c5a4bece92ee8a