Fixed unsafe comparison with a literal. No need to eslint eqeqeq.

Fixed enable method. It was not enabling and activating the collapsible.
This was detected on Jasmine unit testing.

Minor repositioning to this.options.disabled on disable method for
consistency purposes with enable method.

Author: Carlos Lizaga

lib/web/mage/collapsible.js

@@ -243,7 +243,7 @@ define([
                 });
 
             // For collapsible widget only (not tabs or accordion)
-            if (this.header.parent().attr('role') != 'presentation') { //eslint-disable-line eqeqeq
+            if (this.header.parent().attr('role') !== 'presentation') {
                 this.header
                     .parent()
                     .attr('role', 'tablist');
@@ -316,9 +316,9 @@ define([
          * Disable.
          */
         disable: function () {
+            this.options.disabled = true;
             this._off(this.trigger);
             this.forceDeactivate();
-            this.options.disabled = true;
 
             if (this.options.disabledState) {
                 this.element.addClass(this.options.disabledState);
@@ -330,12 +330,14 @@ define([
          * Enable.
          */
         enable: function () {
-            this._on(this.trigger, this.events);
             this.options.disabled = false;
+            this._on(this.trigger, this.events);
+            this.forceActivate();
 
             if (this.options.disabledState) {
                 this.element.removeClass(this.options.disabledState);
             }
+            this.trigger.attr('tabIndex', 0);
         },
 
         /**