Improve potential NPE problem

 - Move CarrierConfigCache initialization to make sure the instance
   created.

Flag: EXEMPT bug fix
Fix: b/409841639
Test: atest pass
(cherry picked from commit 00ab92f97f2c04ca9f604f282542ffd9680f27fc)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:9c2c6745859027b54628bea81a153856e2d8c753)
Merged-In: I07bf9eca1d271d0f38c4d12cd8e04d8a6d4623ed
Change-Id: I07bf9eca1d271d0f38c4d12cd8e04d8a6d4623ed