Generate errors for the FlowMods about flow_manager HOT 4 OPEN

We'll generate:

• error 404 if the DPID does not exist
• error 400 if the body is malformed (invalid fields)
• error 400 if any of the values can't be applied to the flowmod

from flow_manager.

Invalid fields or fields with invalid values are not yet treated.

from flow_manager.

If an inexistent field (like an invalid or not implemented action) is sent, a 500 error is returned. A better error code should be returned in such cases.

from flow_manager.

We'll generate:

• error 404 if the DPID does not exist
• error 400 if the body is malformed (invalid fields)
• error 400 if any of the values can't be applied to the flowmod

When testing the last item, to see what was returned when an invalid value was sent (I tried a string where an integer is required) and the return code was 200. Kytos log showed a PackException when trying to pack the string to integer.
So, when the FlowMod is instantiated, the values are not validated, so no error occurs, the FlowMod is put in the controller's buffer and flow_manager returns no error code. The controller, asynchronously, reads the FlowMod from the buffer and, when trying to pack it, receives a PackException. The error is never returned to the user and the controller crashes.

from flow_manager.