Revert "testutil/registry: remove unused WithStdout(), WithStErr() opts"

This reverts commit 1f21c4dd05.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

testutil/registry/ops.go

@@ -1,5 +1,7 @@
 package registry
 
+import "io"
+
 // Schema1 sets the registry to serve v1 api
 func Schema1(c *Config) {
 	c.schema1 = true
@@ -24,3 +26,17 @@ func URL(registryURL string) func(*Config) {
 		c.registryURL = registryURL
 	}
 }
+
+// WithStdout sets the stdout of the registry command to the passed in writer.
+func WithStdout(w io.Writer) func(c *Config) {
+	return func(c *Config) {
+		c.stdout = w
+	}
+}
+
+// WithStderr sets the stdout of the registry command to the passed in writer.
+func WithStderr(w io.Writer) func(c *Config) {
+	return func(c *Config) {
+		c.stderr = w
+	}
+}