Fixed to show gtl buttons on sub-list views for a Tenant.

- Removed unused 'no_toggle_dash_buttons' variable from top of the view file.
- Added cloud_tenant to list of screens that need to render gtl buttons, moved the check into helper to determine whether to render gtl_view_tb or not

https://bugzilla.redhat.com/show_bug.cgi?id=1140357
Removed tabs and fixed indentations in the view file.

https://bugzilla.redhat.com/show_bug.cgi?id=1140357
Added missing download_data route

https://bugzilla.redhat.com/show_bug.cgi?id=1140357
converted view_buttons.html to HAML.

Moved list of layout that render gtl toolbar into a constant.

https://bugzilla.redhat.com/show_bug.cgi?id=1140357
Merge pull request #557 from h-kataria/show_gtl_buttons_on_tenants_instances_list_view

Fixed to show gtl buttons on sub-list views for a Tenant.