Change the flatten-maven-plugin so it's compatible with mvn deploy

[jacobdotcosta]

When launching the build in PNC with mvn deploy the flatten-maven-plugin is not applied. Make the required changes so this plugin is applied on both builds.

[gytis]

Should I wait until we're done with the 2.2.6 before pushing the change to the sb-2.2.x branch as discussed yesterday?

[jacobdotcosta]

Yes, the fix should only be applied after 2.2.6 is released.