VisibilityFilter deepCopy after Init

[loganasherjones]

Describe the bug
The user VisibilityFilter class will typically NPE if deepCopy is called and then accept is called on the copy.

Versions (OS, Maven, Java, and others, as appropriate):

• Affected version(s) of this project: All
• OS: N/A
• Others: N/A

To Reproduce

The following unit test proves the problem

public void testDeepCopyAfterInit() throws IOException {
    IteratorSetting is = new IteratorSetting(1, VisibilityFilter.class);
    VisibilityFilter.setAuthorizations(is, new Authorizations("abc"));
    Map<String,String> opts = is.getOptions();
    Filter filter = new VisibilityFilter();
    TreeMap<Key,Value> source = new TreeMap<>();
    filter.init(new SortedMapIterator(source), opts, null);
    Filter copyFilter = (Filter) filter.deepCopy(null);
    Key k = new Key("row", "cf", "cq", "abc");
    assertTrue(copyFilter.accept(k, new Value()));
  }

Running this test on 1.X/2.X/3.X will result in an NPE because deepCopy is not implemented for the VisibilityFilter.

Expected behavior
copyFilter.accept(k, new Value()); should return true, not throw an NPE.

Additional context

I'll submit a PR momentarily to demonstrate a possible fix.