Remove requirements style check

This is incorrect and should never have been added.  The order of
lines in requirements files affects the pip dependency resolver.
Therefore, while it's nice to add new packages in alphabetical
order, it must not be required.

Move pbr to the top of the list as it should always be installed
first.  Move hacking to the top of the test-requires list.

Change-Id: I81f7e75b77baccd12d9660dc009f30f2f2c891bc
Merge "Remove requirements style check"