Make sure the "next" URL is in the same origin as Horizon before
redirecting to it.
Conflicts:
horizon/test/unit/workflows/test_workflows.py
Change-Id: I06b2bfc8e3638591615547780c3fa34b0abe19f6
Closes-bug: #1865026
(cherry picked from commit 252467100f)
(cherry picked from commit baa370f843)