Fix MultiSelect on Android.

1. Avoid automatically applying the multiple property to <select> node.
Fixes Android < 4.4 failure where all but first selected value is lost when widget is initialized.

2. Workaround Android bug where clearing one <option>'s selected prop sets another
<option> to be selected, see https://code.google.com/p/android/issues/detail?id=68285.

Fixes #17840.
fix spurious test timeouts on Android, fixes #17849