Fix runtime reboot when connecting to a A2DP headset and

user toggles BT state.

Bug:2607218

This happens when Bluetooth is turned off, and when the headset is
still trying to connect. We get the connection result of
attempt before Bluetooth was toggled. We need to ignore this result.

Change-Id: I023406ec6d59880754ca4f1de676d0dce71b13c6