[BZ 1144052] - Setting z-index to auto to all parents of the logout dropdown menu to join its DOM subtree to the global stacking context and make the z-index working again for it. Result is that it will be on the top even if there is a notification. Also hiding the ajax loader gif icon, because it is not needed anymore.

(cherry picked from commit c0ea3f24b62dd3b82367e3a42f18ac6da2206d48)
Signed-off-by: Libor Zoubek <lzoubek@redhat.com>

Conflicts:
	modules/enterprise/gui/coregui/src/main/webapp/org.rhq.coregui.CoreGUI/sc/skins/CoreGUI/skin_styles.css
[BZ 1144052] - On group creation error, info messages are under fadeout window - the z-index css attribute was ignored, because there were two different so called stacking contexts. By setting the z-index to the default value (which is auto) to all related parent elements we prevent creating new stacking contexts. In other words z-index works correctly only for leave elements in the DOM tree, but if we combine different z-indices in one sub-tree it causes strange behavior.

(cherry picked from commit 5ef0baba7378e0f805f2362bdc6c4c4d9cbce7b3)
Signed-off-by: Libor Zoubek <lzoubek@redhat.com>