Remove unneeded randomness when calling ddt.data()

The usage of sets introduces unneeded randomness, and the
utils.deduplicate function can be used instead.

This is a follow-up to similar past changes, see:
I9cbd26016238c25487ac8104c1188cd2cf4f467e
I15bfbf6e1ca604f2bf2fcf12dcd4e67bc728fe5e

Change-Id: I8fce553d927da6d94471ecdf4040bbbb4377d9cf
1 file changed