zebra: Expand v4/v6 route space

zebra: Expand v4/v6 route space

At some scale we eventually run out of room displaying v4/v6 route
totals for `show zebra client summ`:
janelle# show zebra client summ
Name      Connect Time    Last Read  Last Write  IPv4 Routes       IPv6 Routes
--------------------------------------------------------------------------------
bgp           04w0d18h     00:00:19    00:01:2411729127/4052681  2037786/903094

This total over ran the space in just a little over a week of uptime.
Expand to have a bit more room.

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