Reverse time warps have wrong time_scalar

[jminor]

In the test suite OTIO, the time_scalar values on several of the reverse time warps is incorrect. I believe this is a bug in the AAF to OTIO conversion adapter. If so, I'll make a bug report there and link it here.

• Backwards time warps
  • Reverse 100% (frames 99 to 0)
  • Reverse 50% (frames 99 to 50, each 2x) (BUG: time_scalar -0.51 should be -0.50)
  • Reverse 200% (frames 99 to 0, on 2s) (BUG: time_scalar -1.0 should be -2.0)
  • Reverse 30% (BUG: time_scalar -0.31 should be -0.30)
  • Reverse 120% (BUG: time_scalar -1.0 should be -1.2)