Revendor github.com/Microsoft/hcsshim

1. Revendors github.com/Microsoft/hcsshim to the latest known good commit.
This includes numerous bug fixes and improvements.

2. Vendors indirect dependency on go.opencensus.io since hcsshim now uses trace
correlation.

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>

vendor/github.com/Microsoft/hcsshim/internal/schema2/attachment.go

@@ -10,7 +10,6 @@
 package hcsschema
 
 type Attachment struct {
-
 	Type_ string `json:"Type,omitempty"`
 
 	Path string `json:"Path,omitempty"`