Use references in GATT client/server API (2/3)

This allows to get rid of some unnecessary null checks, and guarantee
proper values are passed.

Test: compilation test
Change-Id: I1b790dba0cfc3ab02984c3911d83a6f413a1e7e6
diff --git a/service/test/gatt_client_unittest.cc b/service/test/gatt_client_unittest.cc
index 7527e8b..c3926eb 100644
--- a/service/test/gatt_client_unittest.cc
+++ b/service/test/gatt_client_unittest.cc
@@ -33,11 +33,11 @@
   MockGattHandler() = default;
   ~MockGattHandler() override = default;
 
-  MOCK_METHOD1(RegisterClient, bt_status_t(bt_uuid_t*));
+  MOCK_METHOD1(RegisterClient, bt_status_t(const bt_uuid_t&));
   MOCK_METHOD1(UnregisterClient, bt_status_t(int));
   MOCK_METHOD1(Scan, bt_status_t(bool));
-  MOCK_METHOD4(Connect, bt_status_t(int, const bt_bdaddr_t*, bool, int));
-  MOCK_METHOD3(Disconnect, bt_status_t(int, const bt_bdaddr_t*, int));
+  MOCK_METHOD4(Connect, bt_status_t(int, const bt_bdaddr_t&, bool, int));
+  MOCK_METHOD3(Disconnect, bt_status_t(int, const bt_bdaddr_t&, int));
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MockGattHandler);