checkcommit: don't check out the original commit

checkcommit depended on the output of git branch which it should never
have done since it isn't stable. Looking at the git-prompt.sh code from
git-contrib, getting back to the original state in the way we wanted
would be really hard, so just skip it. checkcommit was always supposed
to be a low-level abstraction of the build process anyway.
Set a timeout for MessageTransportTest.messageHandlerTest
build.xml: Remove dependency on missing target
checkstyle: remove DoubleCheckedLocking test

The DoubleCheckedLocking test has been removed from newer versions of
checkstyle, so remove it to avoid breaking the build.
Merge remote-tracking branch 'zidel/infrastructure_fixes'