BassClient: Convert metadata for addSource op

Instead of realying on the scanned result, use the
passed metadata. This is needed to accept our own
broadcast metadata, as it is not visible in the
scan results.

Bug: 150670922
Sponsor: jpawlowski@
Test: tested manually
Change-Id: I156916747501e70a0b9a53dc42cefda4a5e989d0