Attempt to fix #361

[jonhyman]

@arthurnn I think that the test that existed for this functionality (below) is broken, but in my timebox for today I can't figure out the trace in the mock replica set. I don't see the auth coming in, but also if this test were valid then I'd expect #361 to not be an issue. Thoughts?

context "when credentials exist on the node" do

          before do
            node.instance_variable_set(:@credentials, { database => [ user, pass ]})
            replica_set_node.unauthorized_on_next_message!
          end

          it "retries the operation" do
            expect(read.execute(node)).to_not be_nil
          end
        end

[coveralls]

Coverage decreased (-0.68%) to 93.0% when pulling bfe3ffe on jonhyman:feature/retry-read into 10abbf3 on mongoid:master.

[coveralls]

Coverage decreased (-0.68%) to 93.0% when pulling bfe3ffe on jonhyman:feature/retry-read into 10abbf3 on mongoid:master.

[coveralls]

Coverage decreased (-0.68%) to 93.0% when pulling bfe3ffe on jonhyman:feature/retry-read into 10abbf3 on mongoid:master.

[jonhyman]

#380 merged this in.