Migrate to containerd v1.7.0 and update dependencies

* Updates containerd to v1.7.0 and new binary for 32-bit
Arm OSes.
* Updates Go dependencies - openfaas and external

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

vendor/google.golang.org/grpc/attributes/attributes.go

@@ -19,7 +19,7 @@
 // Package attributes defines a generic key/value store used in various gRPC
 // components.
 //
-// Experimental
+// # Experimental
 //
 // Notice: This package is EXPERIMENTAL and may be changed or removed in a
 // later release.
@@ -69,7 +69,9 @@ func (a *Attributes) Value(key interface{}) interface{} {
 // bool' is implemented for a value in the attributes, it is called to
 // determine if the value matches the one stored in the other attributes.  If
 // Equal is not implemented, standard equality is used to determine if the two
-// values are equal.
+// values are equal. Note that some types (e.g. maps) aren't comparable by
+// default, so they must be wrapped in a struct, or in an alias type, with Equal
+// defined.
 func (a *Attributes) Equal(o *Attributes) bool {
 	if a == nil && o == nil {
 		return true