[sql lab] only show single run query button (#1858)

* only show single run query button, allow async if possible

* only pass the needed props, rather than entire objects to the component

* add simple test

* fix linting

superset/assets/spec/javascripts/explorev2/components/RunQueryActionButton_spec.js

@@ -0,0 +1,34 @@
+import React from 'react';
+import { expect } from 'chai';
+import { describe, it, beforeEach } from 'mocha';
+import { shallow } from 'enzyme';
+
+import RunQueryActionButton
+  from '../../../../javascripts/SqlLab/components/RunQueryActionButton';
+import Button from '../../../../javascripts/components/Button';
+
+describe('RunQueryActionButton', () => {
+  let wrapper;
+  const defaultProps = {
+    allowAsync: false,
+    dbId: 1,
+    queryState: 'pending',
+    runQuery: () => {}, // eslint-disable-line
+    selectedText: null,
+    stopQuery: () => {}, // eslint-disable-line
+  };
+
+  beforeEach(() => {
+    wrapper = shallow(<RunQueryActionButton {...defaultProps} />);
+  });
+
+  it('is a valid react element', () => {
+    expect(
+      React.isValidElement(<RunQueryActionButton {...defaultProps} />)
+    ).to.equal(true);
+  });
+
+  it('renders a single Button', () => {
+    expect(wrapper.find(Button)).to.have.lengthOf(1);
+  });
+});