Bug 18084: (RM follow-up) Fix authentication tests

Bug 18084: (RM follow-up) Fix authentication tests

A change to the way we hide/expose the user menu in the opac resulted in
the authentication selenium tests failing. This was due to the logout
button being identified as hidden under the new code and as such the
logout action not being triggered correctly between each login test. The
was was simply to add an additonal 'click' event called on the menu
button to put the logout link into the visible viewport.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>