zebra: Display instance id as part of `show zebra client summ`

zebra: Display instance id as part of `show zebra client summ`

When displaying `show zebra client summ` when we have instances
running, display the instance number as well.

New Output:

sharpd@eva ~/frr7 (instance_data)> vtysh -c "show zebra client summ"
Name      Connect Time    Last Read  Last Write  IPv4 Routes       IPv6 Routes
--------------------------------------------------------------------------------
ospf[1]       00:00:02     00:00:02    00:00:02       0/0              0/0
ospf[5]       00:00:02     00:00:02    00:00:02       0/0              0/0
sharp         00:00:02     00:00:02    00:00:02       0/0              0/0
static        00:00:02     00:00:02    00:00:02       0/0              0/0
Routes column shows (added+updated)/deleted

Signed-off-by: Donald Sharp <sharpd@nvidia.com>