cri: make swapping disabled with memory limit

OCI runtime spec defines memory.swap as 'limit of memory+Swap usage'
so setting them to equal should disable the swap. Also, this change
should make containerd behaviour same as other runtimes e.g
'cri-dockerd/dockershim' and won't be impacted when user turn on
'NodeSwap' (https://github.com/kubernetes/enhancements/issues/2400) feature.

Signed-off-by: Qasim Sarfraz <qasimsarfraz@microsoft.com>

pkg/cri/opts/spec_linux.go

@@ -448,6 +448,10 @@ func WithResources(resources *runtime.LinuxContainerResources, tolerateMissingHu
 		}
 		if limit != 0 {
 			s.Linux.Resources.Memory.Limit = &limit
+			// swap/memory limit should be equal to prevent container from swapping by default
+			if swapLimit == 0 {
+				s.Linux.Resources.Memory.Swap = &limit
+			}
 		}
 		if swapLimit != 0 {
 			s.Linux.Resources.Memory.Swap = &swapLimit