Disable concurrency on pr tester (#2155)
Disable concurrency on pr tester (#2155)

Point being that we have pr's stuck the check status stage for a long time, where their generated job dsl's can be overriden by new jobs. We need to go back to the old system of sequential builds and a queue system as described in the README of the pr-tester...

Signed-off-by: Morgan Davies <a6c48ac807a6f6af0e502138d851246d0dddd3ec@gmail.com>
karianna/openjdk-build,AdoptOpenJDK/openjdk-build,karianna/openjdk-build,AdoptOpenJDK/openjdk-build