Failed to view the node that has more than 300k children

[xianhengma]

Try to view a node that has

cversion = 312763
dataVersion = 5376
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 219
numChildren = 312763

failed with

KeeperErrorCode = ConnectionLoss for /<node path>

[gitorko]

1. Introduced a property zkSessionTimeout to keep the zk connection open while big nodes are read.
2. Reduced 2 calls to a single call to scan the tree.

With the above changes building of the node structure has improved but the rendering from freemarker is still taking 4-5 mins.