node slice controller should only process valid whereabouts configs

[dougbtv]

If a net-attach-def with a whereabouts configuration was missing ranges, a comparison of the missing property would cause the node slice controller to crash

Given an invalid config, such as:

[fedora@kubecon-demo crds]$ cat ~/poison-nad.yml 
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: poison-conf
spec:
  config: '{
       "name": "whereabouts-shim",
       "cniVersion": "0.3.1",
       "type": "bridge",
       "ipam": {
         "type": "whereabouts"
       }
      }'

We'd have the node slice controller bomb out when it went to make a comparison:

E0403 17:43:44.816992       1 panic.go:115] "Observed a panic" panic="runtime error: index out of range [0] with length 0" panicGoValue="runtime.boundsError{x:0, y:0, signed:true, code:0x0}" stacktrace=<
	goroutine 88 [running]:
[...snip...]
	/go/src/github.com/k8snetworkplumbingwg/whereabouts/pkg/node-controller/controller.go:526
[...snip...]

With line 526, being return conf1.IPRanges[0].Range == conf2.IPRanges[0].Range && conf1.NodeSliceSize == conf2.NodeSliceSize

So, I went added some checks that the range is there, otherwise, don't process it further.

[coveralls]

Pull Request Test Coverage Report for Build 14250727707

Details

• 2 of 9 (22.22%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.06%) to 51.519%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/node-controller/controller.go	2	9	22.22%

Totals
Change from base Build 14244399522:	-0.06%
Covered Lines:	1967
Relevant Lines:	3818

---

💛 - Coveralls

[bpickard22]

/lgtm