Fix test failure due to mishandled merge
Fix test failure due to mishandled merge

In commit 80eced8, the structure of parameters to `elements.Fiber` was
changed. Options such as fiber length are now passed in via
`self.parameters.*` instead of `self.*`. Commit 639b379 which fixed a
test failure precedes that change, and when we merge both as I did in
commit bc4b664, the test no longer works. My bad. On the other hand,
this will be caught by trunk gating which is something that Zuul can do,
and therefore something that we'll have in our upcoming CI, yay!

Fixes: bc4b664
Change-Id: Ifcd8f0bf01e9d91dbef3da1aa7f56f89132d6f48

Telecominfraproject/gnpy