nfc(api): Restore behavior from Android T

When Nfc service is not ready, dont fetch NfcManager to avoid getting
into a state where the app keeps getting a bad NfcManager.

Restoring the fix from aosp/1498599.

Bug: 286025476
Test: Manual tests
Merged-In: I4aaa0a87c38eaddccc566c18b75cd1acedc29d75

Change-Id: I4aaa0a87c38eaddccc566c18b75cd1acedc29d75