Clarify API doc for BluetoothGattServer::addService

Clarify that the caller has to wait for onServiceAdded callback before
calling BluetoothGattServer::addService again.

Bug: 72717069
Test: Compile
Change-Id: I20b031c724ba64bfd71cf10e58e587f69e4a2555
diff --git a/core/java/android/bluetooth/BluetoothGattServer.java b/core/java/android/bluetooth/BluetoothGattServer.java
index 4ed2500..ef1b0bd 100644
--- a/core/java/android/bluetooth/BluetoothGattServer.java
+++ b/core/java/android/bluetooth/BluetoothGattServer.java
@@ -701,10 +701,14 @@
      * <p>If the local device has already exposed services when this function
      * is called, a service update notification will be sent to all clients.
      *
+     * <p>The {@link BluetoothGattServerCallback#onServiceAdded} callback will indicate
+     * whether this service has been added successfully. Do not add another service
+     * before this callback.
+     *
      * <p>Requires {@link android.Manifest.permission#BLUETOOTH} permission.
      *
      * @param service Service to be added to the list of services provided by this device.
-     * @return true, if the service has been added successfully
+     * @return true, if the request to add service has been initiated
      */
     public boolean addService(BluetoothGattService service) {
         if (DBG) Log.d(TAG, "addService() - service: " + service.getUuid());