Fixed pod's cpu & mem resource setters helpers. (#608)

The original implementation was overwriting any req/limit that was
previosly set for the other resources. For instance, test cases
doing this didn't work properly:

  pod.RedefineWithCPUResources(testPod, "1", "1")
  pod.RedefineWithMemoryResources(testPod, "512Mi", "512Mi")

The call to pod.RedefineWithMemoryResources() was zero-ing the cpu
req/limits that was just set before ("1", "1") as it was creating a new
empty container.Resources field (corev1.ResourceRequirements{}).

The new implementations don't overwrite other reqs/limits values, it
justs sets/overwrite the corresponding ones (cpu/mem).

The affected test cases were passing until now because a bug in the cert
suite code in the function AreCPUResourcesWholeUnits() that was wrongly
returning "true" when the cpu reqs/limit were not set. It was fixed
here:
redhat-best-practices-for-k8s/certsuite#1631

tests/utils/pod/pod.go

@@ -102,27 +102,35 @@ func RedefineWithPVC(pod *corev1.Pod, volumeName string, claimName string) {
 
 func RedefineWithCPUResources(pod *corev1.Pod, limit string, req string) {
 	for i := range pod.Spec.Containers {
-		pod.Spec.Containers[i].Resources = corev1.ResourceRequirements{
-			Limits: corev1.ResourceList{
-				corev1.ResourceCPU: resource.MustParse(limit),
-			},
-			Requests: corev1.ResourceList{
-				corev1.ResourceCPU: resource.MustParse(req),
-			},
+		containerResources := &pod.Spec.Containers[i].Resources
+
+		if containerResources.Requests == nil {
+			containerResources.Requests = corev1.ResourceList{}
 		}
+
+		if containerResources.Limits == nil {
+			containerResources.Limits = corev1.ResourceList{}
+		}
+
+		containerResources.Requests[corev1.ResourceCPU] = resource.MustParse(req)
+		containerResources.Limits[corev1.ResourceCPU] = resource.MustParse(limit)
 	}
 }
 
 func RedefineWithMemoryResources(pod *corev1.Pod, limit string, req string) {
 	for i := range pod.Spec.Containers {
-		pod.Spec.Containers[i].Resources = corev1.ResourceRequirements{
-			Limits: corev1.ResourceList{
-				corev1.ResourceMemory: resource.MustParse(limit),
-			},
-			Requests: corev1.ResourceList{
-				corev1.ResourceMemory: resource.MustParse(req),
-			},
+		containerResources := &pod.Spec.Containers[i].Resources
+
+		if containerResources.Requests == nil {
+			containerResources.Requests = corev1.ResourceList{}
 		}
+
+		if containerResources.Limits == nil {
+			containerResources.Limits = corev1.ResourceList{}
+		}
+
+		containerResources.Requests[corev1.ResourceMemory] = resource.MustParse(req)
+		containerResources.Limits[corev1.ResourceMemory] = resource.MustParse(limit)
 	}
 }