title: Value of stats.FullCount is wrong when AQL IN operator is used
body: <p>ArangoDB3-3.7.2_win64
  arangodbJavaDriver=6.7.5</p>
  <p>Assuming collection has more than 100 documents, the following AQL query through the Java driver using AqlQueryOptions().fullCount(true) returns the expected values in stats.fullCount:</p>
  <pre><code>FOR a IN SomeCollection FILTER a.field = @p1 SORT a.field ASC LIMIT 0,100 RETURN a
  </code></pre>
  <p>But a similar query using the IN operator the value of stats.fullCount is unexpectedly 100:</p>
  <pre><code>FOR a IN SomeCollection FILTER a.field IN [@p1, @p2] SORT a.field ASC LIMIT 0,100 RETURN a
  </code></pre>
  <p>Oddly, when I downgrade to ArangoDB3-3.6.3_win64 both queries work as expected and return the correct value in stats.fullCount</p>
  <p>Can the correct functionality be restored?</p>