packer/template: Remove name from builder rawConfig

This prevents the builder from rejecting the name (which it doesn't
know about) when validating the config.

packer/template.go

@@ -161,6 +161,10 @@ func ParseTemplate(data []byte) (t *Template, err error) {
 			continue
 		}
 
+		// Now that we have the name, remove it from the config - as the builder
+		// itself doesn't know about, and it will cause a validation error.
+		delete(v, "name")
+
 		raw.rawConfig = v
 
 		t.Builders[raw.Name] = raw