pfSelect - destroy the selectpicker when the directive is destroyed

Since patternfly 3.8, the structure of the HTML generated by the selectpicker has changed, and removing the original select element no longer necessarily removes the selectpicker div that's actually visible.

This makes pf-select explicitly destroy the selectpicker when the element with that pf-select is going away.

(Related to ManageIQ/manageiq#11893)

Author: himdel

src/select/select.js

@@ -81,6 +81,10 @@ angular.module('patternfly.select', []).directive('pfSelect', function ($timeout
         });
       };
 
+      var selectpickerDestroy = function () {
+        element.selectpicker('destroy');
+      };
+
       element.selectpicker(scope.selectPickerOptions);
 
       ngModel.$render = function () {
@@ -101,6 +105,8 @@ angular.module('patternfly.select', []).directive('pfSelect', function ($timeout
       }
 
       attrs.$observe('disabled', selectpickerRefresh);
+
+      scope.$on('$destroy', selectpickerDestroy);
     }
   };
 });