Incorrect Javadoc.
[FIXED JENKINS-22560] Avoid deadlock by making AbstractBuild.runMixIn final.
(Forgot that Run’s are unmarshalled in place after a special constructor is called, so there is no need for readResolve or other tricks.)
Also calling RunListener.onDeleted outside of the Run lock to avoid problems with things like ChangeLogHistoryRunListener.
need to explicitly set unprotected security-constraint to /*
or servlet container applies form-login to _all_ URLs 
(detected on tomcat 7.0.50)