Fix the distro tree view selenium test which was broken by 3c27d4b

In commit 3c27d4b, a trailing '/' is added to distro tree url if it
is not present, but the selenium test is not updated accordingly.

Change-Id: Ie6d4802bd0c157682ddedcdc6b19e2ccd03ff289
Merge "Fix the distro tree view selenium test which was broken by 3c27d4b" into develop