fix scale offset applied twice

[haileyajohnson]

fix scale offset applied twice

remove extra calls to convert for performance

[tdrwenski]

Great job getting this done! 🎉 Do you think it's easy to add a test for the scale/offset applied twice to time axes bug? Some of this code may be hard to unit test but we could always add one to the TDS/ NCSS if that's easier.

[haileyajohnson]

The scale/offset applied twice by nccs and the TDS bug is being tested already by all the tests that check that the scale and offset properties are removed, but I was also planning on putting a test in the TDS. The thing with the time axes calling read and convert over and over is kinda hard to test because it doesn't actually change any results, so for me to test it I had to manually count how many times that code was hit...