This problem occurs when you're testing a locally built JBT or JBDS install, because JOB_NAME is not set unless it's built in Jenkins:

!MESSAGE Unable to report download statistics due to invalid URL: http://download.jboss.org/jbosstools/usage/installs/8.0.0-SNAPSHOT/Beta3/${JOB_NAME}/Beta3-v20140605-0424 suffix: org.jboss.tools.ws.feature

Might as well just filter out the JOB_NAME entirely in this case and replace it with something like "local", eg.,

http://download.jboss.org/jbosstools/usage/installs/8.0.0-SNAPSHOT/Beta3/local/Beta3-v20140605-0424