Use slot ID directly for phone account sort order

Bug: 169153499
Test: atest TelecomUnitTests:PhoneAccountRegistrarTest
Change-Id: I59d836e3fe0c756f258c3b7cbe308ce9ec9a0bd9
Merged-In: I59d836e3fe0c756f258c3b7cbe308ce9ec9a0bd9
1 file changed