Refactor: Replace AServiceManager_getService with waitForService

Replaced the deprecated AServiceManager_getService with the recommended
AServiceManager_waitForService. This avoids a potential 5-second poll,
improving test performance and reliability.

Bug: 424274846
Test: atest VtsHalBluetoothAudioTargetTest
Flag: EXEMPT TEST_ONLY
Change-Id: I21cded5baa10dcf1568704bdac014c21c9b65c6b
1 file changed