[nearby] Returns error code for startBroadcast if there is an existing broadcast

Fix: 294461081
Test: -m
Ignore-AOSP-First: nearby_not_in_aosp_yet
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:7b40aa36e8419e134c8171e22a7fa2a2d3bf85a7)
Merged-In: Icc3227ec5aa7d0ea7d33b7100ef131928577b5a7
Change-Id: Icc3227ec5aa7d0ea7d33b7100ef131928577b5a7
2 files changed