Fix some startup issues now that we use cluster size

- Change max cluster size to size of largest cluster
- Cleanup some reading of params
- Catch when ONOS isn't fully started

Change-Id: I5b2ca791046bd4061d31355276958ead39f8b65c
(cherry picked from commit ace1f317e19fd50924e78e53b566d69db23f5683)
diff --git a/TestON/drivers/common/cli/onosdriver.py b/TestON/drivers/common/cli/onosdriver.py
index 18540f0..3ac31dd 100755
--- a/TestON/drivers/common/cli/onosdriver.py
+++ b/TestON/drivers/common/cli/onosdriver.py
@@ -65,10 +65,10 @@
             # The 'nodes' tag is optional and it is not required in .topo file
             for key in self.options:
                 if key == "home":
-                    self.home = self.options[ 'home' ]
+                    self.home = self.options[ key ]
                 elif key == "nodes":
                     # Maximum number of ONOS nodes to run, if there is any
-                    self.maxNodes = int( self.options[ 'nodes' ] )
+                    self.maxNodes = int( self.options[ key ] )
                 elif key == "web_user":
                     self.webUser = self.options[ key ]
                 elif key == "web_pass":