CLI crashes when node command includes name of switch

[benfrankel]

Expected/Desired Behavior:

Mininet should not crash when a command that is run on a node includes (as an arg) the name of a switch that has inNamespace set to False.

Actual Behavior:

Mininet crashes.

Detailed Steps to Reproduce the Behavior:

1. Start Mininet with a configuration that includes a switch with inNamespace=False.
2. Suppose the switch is named switch1.
3. In the Mininet CLI, run the command <node> echo switch1 where <node> is the name of any node.

Additional Information:

The CLI crashes when it tries to access self.controlIntf inside of Switch.defaultIntf():

https://github.com/mininet/mininet/blob/master/mininet/node.py#L919

This happens because self.controlIntf may not be defined if self.inNamespace is set to False, as can be seen in Switch.__init__:

https://github.com/mininet/mininet/blob/master/mininet/node.py#L896

The call to Switch.defaultIntf() is triggered by the CLI trying to replace node args with their IP addresses here:

https://github.com/mininet/mininet/blob/master/mininet/cli.py#L419

To resolve this, Switch.defaultIntf() could be changed to expect an undefined self.controlIntf and not crash, or self.controlIntf could be set to None in Switch.__init__ if self.inNamespace is False.

EDIT: If the node -> IP translation isn't needed for the command, the user can put the node's name in single quotes as a workaround.