Make CardEmulation APIs work even if NFC is off.

Previously we wouldn't index HCE services at all
if NFC was off. This created some weird dependency
that apps would have to check whether NFC was enabled
before being able to trust the APIs, and that could
result in tricky race conditions as well.

Bug: 11023618
Change-Id: I3cbcfcf43fe26d0d878fac75ece51c9e81f7220d