Multiple firing of moveStart/moveEnd events when getting camera heading, pitch, roll

1. A concise explanation of the problem you’re experiencing.

Getting the heading, pitch, roll of the camera periodically can cause additional moveStart/moveEnd events to fire.

2. A minimal code example. If you’ve found a bug, this helps us reproduce and repair it.
Sandcastle:

https://sandcastle.cesium.com/#c=nVRNb9pAEP0rIy4xUrLYBn9ACGpFOVRKmypJc/JlsYew6nqX7q5JaJT/3vEHhKTtIfXB8s7Me/PmzcKWG9gKfEADF6DwAeZoRVWyuybmneTNca6V40KhOemfZ2pLmJyXaDhhWjBrz5TM1GAAcy2rcllZKHWBBGhrbI4KWR0iXNDVlnqLN44bB7hF5TLVMrFDnPGiWNSpS2EdERhvVancCa28PjxlCgByrayWyKS+906+XN0t4Ob24/VtI/a53zTat1qo4i+NKPpfbRZfPzVN3ibPuudYAdnyTUsJ3DkjlpVDC3oFbo17L0mW2YFFYioyZdF9Vg7NlkuPFFzMOhGvDWdr5IVQ960GaN/U6bvKdVnSNOA0CJUb5BabZiuDPytU+Y6EwMNa5Gt4WQEnd/YucYOAj5iT0oIdiF933wiXr8//kTQ0bT3+KQS+7+9NWDyWfCMRNtqK2l0SRUJyXlm0L0oOuyL5BjfISYTcwUoYZIfNreTuVnudLQVaJxSvKSf7SzwnJvriashWRpfXZBVX1jvzmT+Kg9AfJeOhn/hBEqWnLcs7HmIJgihNw8gPgjQdhXESv58lTJIojlgYJaNwOIzHYb/j0EbQ+rp5nl54u4VPIGZhOgzSiCYIknGUHjdv9jKBs4BFiZ+M4yGJG4/ScXxcVO9nAn4beO7uae+0N7VuJ3HWxj+IcqPpZlRGeowNHJYbScuwg2WV/0DHcmtr2HSwB00LsQVRXGS9N38dWQ9yya2lzKqS8kb8wqw3mw6o/hVM6mbAK/o1SL6rS9bB7LINMsamAzr+iXJayyU3R4y/AQ

4. The Cesium version you’re using, your operating system and browser.

Cesium 1.62,****Linux, Chrome/Firefox