bluetooth: att: Fix indication handling

Zephyr device that is not a GATT Client, should ignore indication.

An Android device may send an indication even if Zephyr
device does not support GATT Client role. In that case, the sent
error response was improperly matched to subsequent GATT request
of the Android device which caused issues.

Signed-off-by: Marek Pieta <Marek.Pieta@nordicsemi.no>