CommandBar does not render tooltipHostProps.content with iconOnly mod…

…e as true (#14323)

#### Pull request checklist

- [x] Addresses an existing issue: Fixes #14310
- [ ] Include a change request file using `$ yarn change`

#### Description of changes

CommandBar does not render tooltipHostProps.content with iconOnly=true, when text/name is not available in ICommandBarItemProps

#### Focus areas to test

(optional)

change/office-ui-fabric-react-2020-08-03-14-39-05-master.json

@@ -0,0 +1,8 @@
+{
+  "type": "patch",
+  "comment": "CommandBar: Show tooltipHost.content when iconMode = true even when text/name is provided in commandBarItemProps",
+  "packageName": "office-ui-fabric-react",
+  "email": "[email protected]",
+  "dependentChangeType": "patch",
+  "date": "2020-08-03T21:39:05.655Z"
+}

packages/office-ui-fabric-react/src/components/CommandBar/CommandBar.base.tsx

@@ -169,7 +169,7 @@ export class CommandBarBase extends React.Component<ICommandBarProps, {}> implem
       onClick: this._onButtonClick(item),
     };
 
-    if (item.iconOnly && itemText !== undefined) {
+    if (item.iconOnly && (itemText !== undefined || item.tooltipHostProps)) {
       return (
         <TooltipHost content={itemText} {...item.tooltipHostProps}>
           {this._commandButton(item, commandButtonProps)}