Get rid of meaningles GATT client error log

Right now we often get this error in logs:

E bt_btif_gattc: btif_gattc_upstreams_evt: Unhandled event (7)!

This is often misinterpreted during log analysis as error, where this
really means just uninteresting event we don't want to handle.

Change-Id: Ia7804b2e1802a117198a31e025d05a80f973e896