PLF-5372 : UIGroupsNavigationPortlet: Slowness in readNavigationsAndCache() method
PLF-5372 :  UIGroupsNavigationPortlet: Slowness in readNavigationsAndCache() method (fix functional regression)
PLF-5372: Slowness when read navigations and cache in Group Navigation

Problem analysis
	- Load the UserNode for all types of navigation (SITE, GROUP and USER) which is not necessary. Only group nav are needed for this portlet.

Fix descrption:
	- Only load group navigation and UserNode only for each group navigation.