Fix a test related to GATT client that could never succeed

Caught by Error Prone:
warning: [CollectionIncompatibleType] Argument 'clientIf' should not be
passed to this method; its type int is not compatible with its
collection's type argument AdvertiseClient.

Bug: 27723540
Change-Id: I395b17a46c3734afd0f49866b7aa0bd0f1c6cef4
(cherry picked from commit c6064cce)