Fixes to allow for configuring the host ip to be used when communication w/ nodes

Probably not a real elegant approach, but the configs don't really make a distinction of the current node config.  Anyway, by default it will try to pull a "host" value from the selenium_grid_extras_config.json otherwise it checks the host value in the first node config (if it is a node) or first hub config (if it is a hub).  If nothing is found, it defaults back to OS IP value.