Update Jackson to 2.8.5+

[tlrx]

Jackson's YAML readers (and writers) have concurrency issues when two instances try to parse (or generate) some content. They basically share a same thread local buffer, and that can make the result completely wrong.

The parsing issue has been fixed in 2.8.5 (see this commit because it is not mentioned in release notes) but our tests still fail with a writing issue.

I created FasterXML/jackson-dataformat-yaml#80 to address the Jackson's issue and this issue to track the update. Once fixed in Jackson we will have to update the dependency on 2.8.6 presumably.