quagga: "set community x:y" needs bounds checking

quagga: "set community x:y" needs bounds checking

Signed-off-by: Daniel Walton <dwalton@cumulusnetworks.com>
Reviewed-by:   Donald Sharp <sharpd@cumulusnetworks.com>
Ticket: CM-10002

superm-redxp-05# conf t
superm-redxp-05(config)# route-map FOO permit 10
superm-redxp-05(config-route-map)# set community ?
  AA:NN  Community number in AA:NN format (where AA and NN are <0-65535>) or local-AS|no-advertise|no-export|internet or additive
  none   No community attribute
superm-redxp-05(config-route-map)# set community 2:2
superm-redxp-05(config-route-map)# set community 2:70000
% Malformed communities attribute
superm-redxp-05(config-route-map)# set community 70000:2
% Malformed communities attribute
superm-redxp-05(config-route-map)#