wasted work in AbstractMapBag.containsAll()

The problem appears in version 3.2.1 and in revision 1489197. I
attached a one-line patch that fixes it.

In method "AbstractMapBag.containsAll", the loop over
"other.uniqueSet()" should return immediately after "result" becomes
"false", because "result = result && contains;" can never become
"true" again. All the iterations after "result" becomes "false" do
not perform any useful work, at best they just set "result" again to
"false".