ENYO-3521: change the button name from "cancelWaitPopup" to "cancelBuildButton".
ENYO-3521: the hidding of the cancelBuildButton is done when the Popup is hidden.
ENYO-3521: use an ENYO function to abort a build.
Merge pull request #666 from enyojs/ENYO-3521

ENYO-3521: fix an undesired apparition of the button "cancel" on the wait Pop-up during the 1st phase of PGB action.