Save some memory in CarrierPrivilegesTracker

Reduce the initial size of some ArraySets so that they
only initially allocate capacity for 1 instead of 4 since
in most cases there will only be one value.

Bug: 162182054
Test: atest CarrierPrivilegesTrackerTest; # (no behavior change)
Change-Id: I82f6adc3d0d16e505fe3405fc4a5e1345d0010ce