Fix sortableTable hover effect and searchTab onClick

fix brave#4099

Auditors: @bbondy

Test Plan:

1. Go to "about:preferences#search"
2. There should be hover effect when hovering on row
3. Should be able to swtch default search engine

js/about/preferences.js

@@ -616,7 +616,7 @@ class SearchTab extends ImmutableComponent {
  }
 
  hoverCallback (rows) {
- this.props.onChangeSetting(settings.DEFAULT_SEARCH_ENGINE, rows[1].props.children.props.name)
+ this.props.onChangeSetting(settings.DEFAULT_SEARCH_ENGINE, rows[1].value)
  }
 
  render () {

js/components/sortableTable.js

@@ -99,7 +99,8 @@ class SortableTable extends ImmutableComponent {
  const rowAttributes = this.getRowAttributes(row, i)
  return <tr {...rowAttributes}
  data-context-menu-disable={rowAttributes.onContextMenu ? true : undefined}
- className={this.hasRowClassNames ? this.props.rowClassNames[i] : undefined}>{entry}</tr>
+ className={this.hasRowClassNames ? this.props.rowClassNames[i] + ' ' + rowAttributes.className
+ : rowAttributes.className}>{entry}</tr>
  })
  }
  </tbody>