Fixed the incorrect dead code removal

Carrier key download manger initialization code was incorrectly
removed during code clean up. Added it back.

Fixes: 446229607
Test: atest FrameworksTelephonyTests
Test: Basic telephony functionality tests
Flag: EXEMPT BUGFIX
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:016cd830452932017be6e7dad4d82ad4ee7d2e67
Merged-In: I64453cd18d9e9abac4df3f43390000c9c949bd57
Change-Id: I64453cd18d9e9abac4df3f43390000c9c949bd57