getProfileIdsLU uses internal UserProperties

getProfileIdsLU was calling isProfileHidden(), which was using the
external method for fetching the UserProperties. This meant creating a
needless copy of the Properties and, even worse, did a permission check
with the LU lock held. We can just use the internal version.

Bug: 410481999
Flag: EXEMPT bug fix
Test: UserManagerServiceTest
Change-Id: I403cf55bb30b36cfe49916edc2bb17b049abd32c