Build tweaks

[shemnon]

PR description

JDK smoke tester says corretto didn't like the 2.8.0 version, so roll it back.

Caused by: java.io.IOException: Cannot run program “git” (in directory “/var/jenkins-slave-workspace/workspace/Pantheon-jdk-smoke-test”): error=2, No such file or directory
    at net.researchgate.release.cli.Executor.exec(Executor.groovy:35)
    at net.researchgate.release.cli.Executor$exec.call(Unknown Source)
    at net.researchgate.release.PluginHelper.exec(PluginHelper.groovy:61)
    at net.researchgate.release.PluginHelper$exec$0.callCurrent(Unknown Source)
    at net.researchgate.release.GitAdapter.gitCurrentBranch(GitAdapter.groovy:192)
    at net.researchgate.release.GitAdapter.<init>(GitAdapter.groovy:56)
    ... 151 more
Caused by: java.io.IOException: error=2, No such file or directory
    ... 157 more

[ajsutton]

LGTM.