Updated testContextMock() how it checks the bluetooth_connected string.
Bug: 72317067
Test: Unit test updated:
make ROBOTEST_FILTER=BluetoothDetailsHeaderControllerTest \
RunSettingsRoboTests
Manual: two headsets and switching the active device
Change-Id: I3db178d71543e4dfa437544350c58241860ae703
Merged-In: I3db178d71543e4dfa437544350c58241860ae703
(cherry picked from commit b58b006e44)