Influx: Make variable query editor input uncontrolled (#29968)

public/app/plugins/datasource/influxdb/components/VariableQueryEditor.tsx

@@ -35,11 +35,11 @@ export default class VariableQueryEditor extends PureComponent<Props> {
         <InlineFormLabel width={10}>Query</InlineFormLabel>
         <div className="gf-form-inline gf-form--grow">
           <TextArea
-            value={query || ''}
+            defaultValue={query || ''}
             placeholder="metric name or tags query"
             rows={1}
             className="gf-form-input"
-            onChange={e => onChange(e.currentTarget.value)}
+            onBlur={e => onChange(e.currentTarget.value)}
           />
         </div>
       </div>