3.4.0 stat compatibility and dashboard robustness while zk's are restarting

[ezbz]

for 3.4.0 the stat command returns clients without the closing ) modified models.py to account for this fact.

added try/except clauses for various property assignment code with simple defaults so the dashboard won't crash with an error when one of the zookeepers in the ensemble is restarting (versions/latencies were not resolving correctly)