vendor: update buildkit with typed errors support

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

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

@@ -4,12 +4,9 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
-	"os"
-	"strconv"
 	"strings"
 	"sync"
 	"syscall"
-	"time"
 
 	"github.com/Microsoft/hcsshim/internal/cow"
 	"github.com/Microsoft/hcsshim/internal/log"
@@ -21,27 +18,6 @@ import (
 	"go.opencensus.io/trace"
 )
 
-// currentContainerStarts is used to limit the number of concurrent container
-// starts.
-var currentContainerStarts containerStarts
-
-type containerStarts struct {
-	maxParallel int
-	inProgress  int
-	sync.Mutex
-}
-
-func init() {
-	mpsS := os.Getenv("HCSSHIM_MAX_PARALLEL_START")
-	if len(mpsS) > 0 {
-		mpsI, err := strconv.Atoi(mpsS)
-		if err != nil || mpsI < 0 {
-			return
-		}
-		currentContainerStarts.maxParallel = mpsI
-	}
-}
-
 type System struct {
 	handleLock     sync.RWMutex
 	handle         vmcompute.HcsSystem
@@ -215,32 +191,6 @@ func (computeSystem *System) Start(ctx context.Context) (err error) {
 		return makeSystemError(computeSystem, operation, "", ErrAlreadyClosed, nil)
 	}
 
-	// This is a very simple backoff-retry loop to limit the number
-	// of parallel container starts if environment variable
-	// HCSSHIM_MAX_PARALLEL_START is set to a positive integer.
-	// It should generally only be used as a workaround to various
-	// platform issues that exist between RS1 and RS4 as of Aug 2018
-	if currentContainerStarts.maxParallel > 0 {
-		for {
-			currentContainerStarts.Lock()
-			if currentContainerStarts.inProgress < currentContainerStarts.maxParallel {
-				currentContainerStarts.inProgress++
-				currentContainerStarts.Unlock()
-				break
-			}
-			if currentContainerStarts.inProgress == currentContainerStarts.maxParallel {
-				currentContainerStarts.Unlock()
-				time.Sleep(100 * time.Millisecond)
-			}
-		}
-		// Make sure we decrement the count when we are done.
-		defer func() {
-			currentContainerStarts.Lock()
-			currentContainerStarts.inProgress--
-			currentContainerStarts.Unlock()
-		}()
-	}
-
 	resultJSON, err := vmcompute.HcsStartComputeSystem(ctx, computeSystem.handle, "")
 	events, err := processAsyncHcsResult(ctx, err, resultJSON, computeSystem.callbackNumber, hcsNotificationSystemStartCompleted, &timeout.SystemStart)
 	if err != nil {