Updated jackson version to 2.8.11

[tjo]

Please ensure your pull request adheres to the following guidelines:

• Please explain your motives to contribute this change: what problem you are trying to fix, what improvement you are trying to make
• Use the following formatting style: SonarSource/sonar-developer-toolset
• Provide a unit test for any code you changed
• If there is a JIRA ticket available, please make your commits and pull request start with the ticket ID (SONAR-XXXX)

The current jackson-databind version (2.6.6) contains multiple vulnerabilities (FasterXML/jackson-databind#1904) that were fixed in the 2.8.11 version. This also applies to jjwt dependency - jwtk/jjwt#302
This change will override the jackson-databind version pulled by jjwt

Current unit tests should cover compatibility.

This should solve also RSPEC-4544.

[simonbrandhof]

Thanks for the contribution. Ticket was created: https://jira.sonarsource.com/browse/SONAR-10608 and will be fixed in 6.7.4 and 7.2.
Note that the Travis build for external contributions will have to be fixed on our side. Some private credentials make the build fail.

[simonbrandhof]

Patch applied to branch-6.7.