When bt_gatt_client receives 'indication' it sends 'confirmation'.
'confirmation' sending was broken after adding support for 'clones' of
bt_gatt_client. In addition to first bt_gatt_client each clone also
sends 'confirmation'.

# > ACL Data RX: Handle 69 flags 0x02 dlen 27
#       ATT: Handle Value Indication (0x1d) len 22
#         Handle: 0x001f
#           Data: 68656c6c6f2027302e302e302e303a3532353332
# < ACL Data TX: Handle 69 flags 0x00 dlen 5
#       ATT: Handle Value Confirmation (0x1e) len 0
# < ACL Data TX: Handle 69 flags 0x00 dlen 5
#       ATT: Handle Value Confirmation (0x1e) len 0

Extra confirmation sent by clone confuses remote side. When bluetooth
daemon receives extra confirmation it breaks connection.

Attached patch fixes the issue limiting confirmation sending to single
bt_gatt_client.