Fix entitlement failed when device is on CBRS

Tethering may use wrong sub id for entitlement when data
subscription is changed from preferred data sub id to CBRS
sub id. Fix by using the active data sub id for tethering.

Bug: 134994718
Test: -build, flash, boot
      -FrameworkNetTests
      -manual test with carrier SIMs

Change-Id: Icb3f5eeb2319e50b2dc98369ad152988c934da57
Merged-In: Icb3f5eeb2319e50b2dc98369ad152988c934da57