requirements.txt: Bump tornado version to 3.2.2.
requirements.txt: Bump tornado version to 3.2.2.

Change-Id: I563a97affc63e04195dbfa1060b9b34db504b4d3

joyxu/kernelci-backend,kernelci/kernelci-backend,joyxu/kernelci-backend,kernelci/kernelci-backend,joyxu/kernelci-backend