Fix "Add Association" and "Delete Association" displaying

This patch adds "ajax-modal" class to LBaaS "Add Health Monitor"
and "Delete Health Monitor" links. So these links open pop-up
windows with "Cancel" and "Add"/"Delete" buttons.

Fixes bug 1212978

Change-Id: Ie5a02ca07a9ee09abbbfd0b32db5141069e4adbe
Merge "Fix "Add Association" and "Delete Association" displaying"