policy classifier create API needs to validate input

The policy classifier API needs to validate its input
i provided a port range for ICMP and it happily accepted it. This needs to be validated and rejected

Repro
Run rally test with following input file

    "GBPTests.create_policy_classifier": [
        {
            "args": {
                "classifier_args": {
                    "protocol": "icmp",
                    "port_range": "80",
                    "direction": "in"
                }
            },
            "runner": {
                "type": "constant",
                "times": 1,
                "concurrency": 1
            },
            "context": {
                "users": {
                    "tenants": 1,
                    "users_per_tenant": 1
                },
            }
        }
    ],
rally -v task start test.json
+---------------------------------------------------------------------------------------------------+
| Response Times (sec) |
+------------------------------+-------+--------+--------+--------+-------+-------+---------+-------+
| action | min | median | 90%ile | 95%ile | max | avg | success | count |
+------------------------------+-------+--------+--------+--------+-------+-------+---------+-------+
| gbp.create_policy_action | 0.191 | 0.191 | 0.191 | 0.191 | 0.191 | 0.191 | 100.0% | 1 |
| gbp.create_policy_classifier | 0.015 | 0.015 | 0.015 | 0.015 | 0.015 | 0.015 | 100.0% | 1 |
| total | 0.206 | 0.206 | 0.206 | 0.206 | 0.206 | 0.206 | 100.0% | 1 |
+------------------------------+-------+--------+--------+--------+-------+-------+---------+-------+