Revert "XE-1046: Upgrade to Selenium 2.12.0"
Revert "XE-1046: Upgrade to Selenium 2.12.0"

This reverts commit 06480b40aa2b505a936c00d5a227a170dbd3fb44 which seem to break some test in test-ui.

xwiki/xwiki-enterprise,xwiki/xwiki-enterprise