RigidbodyConstraints related to rotation doesn't work correctly when trying to rotate object with some ForceMode's. A little bit of rotation is still applied even when constrains are enabled.

To reproduce:

1. Open project.
2. Inspect the script attached to gameobject in the scene.

rigidBody.constraints = RigidbodyConstraints.FreezeAll;
yield return new WaitForFixedUpdate();
rigidBody.AddRelativeTorque(new Vector3(0, 0.5f, 0), ForceMode.Acceleration);
yield return new WaitForFixedUpdate();
Debug.AssertFormat(rigidBody.angularVelocity == Vector3.zero, "{0}", rigidBody.angularVelocity.y);

3. Enter play mode.

Note: You can see in the inspector that the object rotates a little bit and then stops.

4. Exit play mode.
5. Comment line "rigidBody.constraints = RigidbodyConstraints.FreezeAll;".
6. Enter Play.

Note: You can see the same results even though constrains line is commented out.

Expected results: No rotation.
Actual results: Rotation occurs.

Important notes:

1. Same bug occurs when using "RigidbodyConstraints.FreezeRotation" instead of "RigidbodyConstraints.FreezeAll".
2. Same bug occurs when using "ForceMode.VelocityChange" instead of " ForceMode.Acceleration".

Reproduces with: 5.3.6f1; 5.4.3p3; 5.5.0p3; 5.6.0b3;