Inherit StopSignal from Dockerfile.

Make sure the image configuration is not overriden by the default
value in the `create` flag.

Signed-off-by: David Calavera <david.calavera@gmail.com>
Upstream-commit: a252516ec19c9c83055a882da894712f2e812ecc
Component: engine

components/engine/daemon/commit.go

@@ -89,6 +89,10 @@ func merge(userConf, imageConf *containertypes.Config) error {
 			userConf.Volumes[k] = v
 		}
 	}
+
+	if userConf.StopSignal == "" {
+		userConf.StopSignal = imageConf.StopSignal
+	}
 	return nil
 }