Fix the GATT re-discovery failure when GATT service discovery is ongoing

If 'BTA_GATTC_Refresh' is called when GATT service discovery is ongoing, GATT service discovery should be restarted after GATT service discovery is completed.
But it cannot be restarted actually because of missing set 'auto_update' state.
This patch set 'auto_update' state to start discovery again correctly.

Change-Id: Id18f04705fef253261e52836849e4e6020e42a05