This patch:
* re-enables 3 previously disabled integration tests for users
crate/delete, keypairs and floating ips
* updates selectors for sidebar menu and user context menu
* adds some selenium specific classes to different sidebar menus in
order integration tests could check open/closed state of
dashboard/panel group sections (horizon.selenium.js)
* updates default path to horizon (which is now /dashboard at
devstack)
* temporarily disables Sahara integration tests
Related-Bug: #1467950
Implements blueprint: integration-tests-hardening
Change-Id: I688eb7d72d5504cb55b977d85435019e3f69323f