go.mod: Update hcsshim to v0.8.21

This version brings in some bug fixes to layer handling. The actual fix isn't
present in the diff as it's not used here, but the Windows shim is built from
the tag present in go.mod, so the fix will be in the Windows shim on a new release
of Containerd if this tag is in.

Signed-off-by: Daniel Canter <dcanter@microsoft.com>

vendor/github.com/Microsoft/hcsshim/internal/hcs/errors.go

@@ -60,7 +60,7 @@ var (
 	// ErrVmcomputeOperationInvalidState is an error encountered when the compute system is not in a valid state for the requested operation
 	ErrVmcomputeOperationInvalidState = syscall.Errno(0xc0370105)
 
-	// ErrProcNotFound is an error encountered when the the process cannot be found
+	// ErrProcNotFound is an error encountered when a procedure look up fails.
 	ErrProcNotFound = syscall.Errno(0x7f)
 
 	// ErrVmcomputeOperationAccessIsDenied is an error which can be encountered when enumerating compute systems in RS1/RS2
@@ -242,12 +242,11 @@ func makeProcessError(process *Process, op string, err error, events []ErrorEven
 // IsNotExist checks if an error is caused by the Container or Process not existing.
 // Note: Currently, ErrElementNotFound can mean that a Process has either
 // already exited, or does not exist. Both IsAlreadyStopped and IsNotExist
-// will currently return true when the error is ErrElementNotFound or ErrProcNotFound.
+// will currently return true when the error is ErrElementNotFound.
 func IsNotExist(err error) bool {
 	err = getInnerError(err)
 	return err == ErrComputeSystemDoesNotExist ||
-		err == ErrElementNotFound ||
-		err == ErrProcNotFound
+		err == ErrElementNotFound
 }
 
 // IsAlreadyClosed checks if an error is caused by the Container or Process having been
@@ -278,12 +277,11 @@ func IsTimeout(err error) bool {
 // a Container or Process being already stopped.
 // Note: Currently, ErrElementNotFound can mean that a Process has either
 // already exited, or does not exist. Both IsAlreadyStopped and IsNotExist
-// will currently return true when the error is ErrElementNotFound or ErrProcNotFound.
+// will currently return true when the error is ErrElementNotFound.
 func IsAlreadyStopped(err error) bool {
 	err = getInnerError(err)
 	return err == ErrVmcomputeAlreadyStopped ||
-		err == ErrElementNotFound ||
-		err == ErrProcNotFound
+		err == ErrElementNotFound
 }
 
 // IsNotSupported returns a boolean indicating whether the error is caused by

vendor/github.com/Microsoft/hcsshim/internal/hns/hnsendpoint.go

@@ -30,6 +30,7 @@ type HNSEndpoint struct {
 	EnableLowMetric    bool              `json:",omitempty"`
 	Namespace          *Namespace        `json:",omitempty"`
 	EncapOverhead      uint16            `json:",omitempty"`
+	SharedContainers   []string          `json:",omitempty"`
 }
 
 //SystemType represents the type of the system on which actions are done
@@ -57,6 +58,18 @@ type EndpointResquestResponse struct {
 	Error   string
 }
 
+// EndpointStats is the object that has stats for a given endpoint
+type EndpointStats struct {
+	BytesReceived          uint64 `json:"BytesReceived"`
+	BytesSent              uint64 `json:"BytesSent"`
+	DroppedPacketsIncoming uint64 `json:"DroppedPacketsIncoming"`
+	DroppedPacketsOutgoing uint64 `json:"DroppedPacketsOutgoing"`
+	EndpointID             string `json:"EndpointId"`
+	InstanceID             string `json:"InstanceId"`
+	PacketsReceived        uint64 `json:"PacketsReceived"`
+	PacketsSent            uint64 `json:"PacketsSent"`
+}
+
 // HNSEndpointRequest makes a HNS call to modify/query a network endpoint
 func HNSEndpointRequest(method, path, request string) (*HNSEndpoint, error) {
 	endpoint := &HNSEndpoint{}
@@ -79,11 +92,27 @@ func HNSListEndpointRequest() ([]HNSEndpoint, error) {
 	return endpoint, nil
 }
 
+// hnsEndpointStatsRequest makes a HNS call to query the stats for a given endpoint ID
+func hnsEndpointStatsRequest(id string) (*EndpointStats, error) {
+	var stats EndpointStats
+	err := hnsCall("GET", "/endpointstats/"+id, "", &stats)
+	if err != nil {
+		return nil, err
+	}
+
+	return &stats, nil
+}
+
 // GetHNSEndpointByID get the Endpoint by ID
 func GetHNSEndpointByID(endpointID string) (*HNSEndpoint, error) {
 	return HNSEndpointRequest("GET", endpointID, "")
 }
 
+// GetHNSEndpointStats get the stats for a n Endpoint by ID
+func GetHNSEndpointStats(endpointID string) (*EndpointStats, error) {
+	return hnsEndpointStatsRequest(endpointID)
+}
+
 // GetHNSEndpointByName gets the endpoint filtered by Name
 func GetHNSEndpointByName(endpointName string) (*HNSEndpoint, error) {
 	hnsResponse, err := HNSListEndpointRequest()