title: TextInput cursor pointer remains on screen after component unmounts
body: <p>The cursor pointer remains like a ghost from the past after having selected a <code>&lt;TextInput/&gt;</code> in a previous screen. Switching screens doesn't make it go away, pressing it doesn't do anything - it just floats there in the same spot. In fact, the screenshot below had two pointers from the same TextInput but the left one disappeared after a little while, while the other one stuck around (pun intended :) Anyone else experience this?</p>
  
  <p>Environment: </p>
  
  <p>Android 5.1.1</p>
  
  <p>react: 16.3.1</p>
  
  <p>react-native: ~0.55.2</p>
  
  <p><a href="https://i.stack.imgur.com/6blyP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6blyP.png" alt="Screenshot of cursor pointer remaining on screen"></a></p>