message: fix(shell-api): adjust .drop() return value for server changes
  See the server now returns no error when dropping
  non-existent collections.
diff: @@ -847,10 +847,20 @@ describe('Shell API (integration)', function() {
  });
  context('when a collection does not exist', () => {
  + context('pre-7.0', () => {
  + skipIfServerVersion(testServer, '>= 7.0');
  it('returns false', async() => {
  expect(await collection.drop()).to.be.false;
  });
  });
  +
  + context('post-7.0', () => {
  + skipIfServerVersion(testServer, '< 7.0');
  + it('returns true', async() => {
  + expect(await collection.drop()).to.be.true;
  + });
  + });
  + });
  });
  describe('exists', () => {
  @@ -865,8 +875,8 @@ describe('Shell API (integration)', function() {
  });
  context('when a collection does not exist', () => {
  - it('returns false', async() => {
  - expect(await collection.drop()).to.be.false;
  + it('returns null', async() => {
  + expect(await collection.exists()).to.be.null;
  });
  });
  });
  