Update getpwnam() tests to correctly handle new app zygote uids.

The UID range [90000..98999] is used for isolated processes that are
spawned from an application zygote. Otherwise they are identical to
regular isolated processes in the [99000..99999] range. Fix the tests to
match the new range.

Bug: 111434506
Test: atest bionic-unit-tests-static
Change-Id: Id0352f2cf0d21edb04d95f01ea2548e95b62317a