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>

go.mod

@@ -4,7 +4,7 @@ go 1.16
 
 require (
 	github.com/Microsoft/go-winio v0.4.17
-	github.com/Microsoft/hcsshim v0.8.18
+	github.com/Microsoft/hcsshim v0.8.21
 	github.com/containerd/aufs v1.0.0
 	github.com/containerd/btrfs v1.0.0
 	github.com/containerd/cgroups v1.0.1

go.sum

@@ -40,8 +40,8 @@ github.com/Microsoft/go-winio v0.4.17 h1:iT12IBVClFevaf8PuVyi3UmZOVh4OqnaLxDTW2O
 github.com/Microsoft/go-winio v0.4.17/go.mod h1:JPGBdM1cNvN/6ISo+n8V5iA4v8pBzdOpzfwIujj1a84=
 github.com/Microsoft/hcsshim v0.8.6/go.mod h1:Op3hHsoHPAvb6lceZHDtd9OkTew38wNoXnJs8iY7rUg=
 github.com/Microsoft/hcsshim v0.8.16/go.mod h1:o5/SZqmR7x9JNKsW3pu+nqHm0MF8vbA+VxGOoXdC600=
-github.com/Microsoft/hcsshim v0.8.18 h1:cYnKADiM1869gvBpos3YCteeT6sZLB48lB5dmMMs8Tg=
-github.com/Microsoft/hcsshim v0.8.18/go.mod h1:+w2gRZ5ReXQhFOrvSQeNfhrYB/dg3oDwTOcER2fw4I4=
+github.com/Microsoft/hcsshim v0.8.21 h1:btRfUDThBE5IKcvI8O8jOiIkujUsAMBSRsYDYmEi6oM=
+github.com/Microsoft/hcsshim v0.8.21/go.mod h1:+w2gRZ5ReXQhFOrvSQeNfhrYB/dg3oDwTOcER2fw4I4=
 github.com/NYTimes/gziphandler v0.0.0-20170623195520-56545f4a5d46/go.mod h1:3wb06e3pkSAbeQ52E9H9iFoQsEEwGN64994WTCIhntQ=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/PuerkitoBio/purell v1.1.1/go.mod h1:c11w/QuzBsJSee3cPx9rAFu61PvFxuPbtSwDGJws/X0=

integration/client/go.mod

@@ -3,7 +3,7 @@ module github.com/containerd/containerd/integration/client
 go 1.15
 
 require (
-	github.com/Microsoft/hcsshim v0.8.18
+	github.com/Microsoft/hcsshim v0.8.21
 	github.com/Microsoft/hcsshim/test v0.0.0-20210408205431-da33ecd607e1
 	github.com/containerd/cgroups v1.0.1
 	// the actual version of containerd is replaced with the code at the root of this repository

integration/client/go.sum

@@ -41,8 +41,8 @@ github.com/Microsoft/go-winio v0.4.17/go.mod h1:JPGBdM1cNvN/6ISo+n8V5iA4v8pBzdOp
 github.com/Microsoft/hcsshim v0.8.6/go.mod h1:Op3hHsoHPAvb6lceZHDtd9OkTew38wNoXnJs8iY7rUg=
 github.com/Microsoft/hcsshim v0.8.15/go.mod h1:x38A4YbHbdxJtc0sF6oIz+RG0npwSCAvn69iY6URG00=
 github.com/Microsoft/hcsshim v0.8.16/go.mod h1:o5/SZqmR7x9JNKsW3pu+nqHm0MF8vbA+VxGOoXdC600=
-github.com/Microsoft/hcsshim v0.8.18 h1:cYnKADiM1869gvBpos3YCteeT6sZLB48lB5dmMMs8Tg=
-github.com/Microsoft/hcsshim v0.8.18/go.mod h1:+w2gRZ5ReXQhFOrvSQeNfhrYB/dg3oDwTOcER2fw4I4=
+github.com/Microsoft/hcsshim v0.8.21 h1:btRfUDThBE5IKcvI8O8jOiIkujUsAMBSRsYDYmEi6oM=
+github.com/Microsoft/hcsshim v0.8.21/go.mod h1:+w2gRZ5ReXQhFOrvSQeNfhrYB/dg3oDwTOcER2fw4I4=
 github.com/Microsoft/hcsshim/test v0.0.0-20210408205431-da33ecd607e1 h1:pVKfKyPkXna29XlGjxSr9J0A7vNucOUHZ/2ClcTWalw=
 github.com/Microsoft/hcsshim/test v0.0.0-20210408205431-da33ecd607e1/go.mod h1:Cmvnhlie15Ha2UYrJs9EhgSx76Bq9RV2FgfEiT78GhI=
 github.com/NYTimes/gziphandler v0.0.0-20170623195520-56545f4a5d46/go.mod h1:3wb06e3pkSAbeQ52E9H9iFoQsEEwGN64994WTCIhntQ=