zt network data can be incomplete until routes appear

[sarnold]

When networks are created on a ZT node there is a finite amount of time (on the order of seconds) between when the client "sees" the new network and when the network routing data is fully populated. The end result is a possible exception when nodestate.py collects the netStatus data from the cache; note the size of the route list is '0' in the log snippet below:

2020-01-03 01:59:28 UTC node_tools.cache_funcs.get_endpoint_data +52: DEBUG [29823] Entering get_endpoint_data with key_str: net
2020-01-03 01:59:28 UTC node_tools.cache_funcs.get_endpoint_data +60: DEBUG [29823] Appending data for key: net-500000000000000
2020-01-03 01:59:28 UTC node_tools.cache_funcs.get_endpoint_data +63: DEBUG [29823] Leaving get_endpoint_data
2020-01-03 01:59:28 UTC node_tools.cache_funcs.get_net_status +76: DEBUG [29823] net-500000000000000 route list size: 0
2020-01-03 01:59:28 UTC node_tools.helper_funcs.update_state +115: ERROR [29823] update_state exception: list index out of range
2020-01-03 01:59:28 UTC node_tools.data_funcs.do_logstats +32: DEBUG [29823] 13 items currently in cache.
2020-01-03 01:59:29 UTC node_tools.data_funcs.do_logstats +33: DEBUG [29823] Cache items: ['node-500000000000000', 'peer-500000000000000', 'peer-500000000000001', 'peer-500000000000002', 'peer-500000000000003', 'peer-5
00000000000004', 'peer-500000000000005', 'peer-500000000000006', 'moon-500000000000000', 'nstate-500000000000000', 'mstate-500000000000000', 'utc-time', 'net-500000000000000']
2020-01-03 01:59:29 UTC node_tools.data_funcs.do_logstats +31: DEBUG [29823] Leaving update_runner
2020-01-03 01:59:29 UTC node_tools.data_funcs.do_logstats +32: DEBUG [29823] 13 items currently in cache.
2020-01-03 01:59:29 UTC node_tools.data_funcs.do_logstats +33: DEBUG [29823] Cache items: ['node-500000000000000', 'peer-500000000000000', 'peer-500000000000001', 'peer-500000000000002', 'peer-500000000000003', 'peer-5
00000000000004', 'peer-500000000000005', 'peer-500000000000006', 'moon-500000000000000', 'nstate-500000000000000', 'mstate-500000000000000', 'utc-time', 'net-500000000000000']
2020-01-03 01:59:29 UTC node_tools.data_funcs.wrapper +64: INFO [29823] Get data result: ENODATA