title: ag-grid checkbox column checked by renderer
body: <p>I am using ag-grid with checkbox header component to allow select/deselect all rows. Now when I fetch the data for grid, I want to check/uncheck checkbox column on based of some field value. I tried a renderer but it's not working with below code. If I remove 'checkboxSelection' from the column definition, it works perfectly. </p>
  
  <pre><code>  this.gridClientOptions = {
    enableFilter: true,
    enableSorting: true,
    enableColResize: true,
    pagination: true,
    paginationPageSize: 5,
    rowSelection: 'multiple',
    suppressRowClickSelection: true,
    columnDefs: [
        {
          headerName: '',
          width: 40,
          headerCheckboxSelection: true,
          headerCheckboxSelectionFilteredOnly: true,
          checkboxSelection: true,
          cellRenderer: 'selectedClient'
      },
      {headerName: 'Client Code', field: 'clientCode'},
      {headerName: 'Client Name', field: 'clientName'},
      {headerName: 'Group Name', field: 'groupName'},
    ],
    components: {
      'selectedClient': this.selectedClient
    },
    getRowStyle: function(params) {
      if (params.node.rowIndex % 2 === 0) {
          return { background: '#dfffdf' }
      }
    }      
  }
  
  selectedClient(params) {
  return params.data.assignmentId &gt; 0 ? `&lt;input type='checkbox' checked&gt;` : `&lt;input type='checkbox'&gt;`;
    }
  </code></pre>