setAffiliationIds and getAffiliationIds uses set instead of list

Didn't use @remove because java doesn't support two methods differs from
the return type only.

Test: cts-tradefed run cts-dev --module DevicePolicyManager --test com.android.cts.devicepolicy.DeviceOwnerTest#testLockTask_unaffiliatedUser
Test: runtest -x frameworks/base/services/tests/servicestests/src/com/android/server/devicepolicy/DevicePolicyManagerTest.java
Test: cts-tradefed run cts-dev --module DevicePolicyManager  --test com.android.cts.devicepolicy.DeviceOwnerPlusProfileOwnerTest

Change-Id: Ic7c7221ef5e680a6765f028c2ab73d4c2f908c58
Fix: 37622682