Just pull-right dropdown-menu worked for me.
EDIT:
Deprecated .pull-right alignment
Starting with version 3.1, we have deprecated .pull-right in the drop-down menus. To align the menu to the right, use .dropdown-menu-right . Alignment navigation components in the navigation bar use the mixin version of this class to automatically align menus. To undo it, use .dropdown-menu-left .
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