Jetty 9/10 WebSocket memory test

Running on jetty 9

# first terminal 
./start.sh 9
# second terminal
./gradlew --rerun-tasks :loadtest:test
# completes

Running on jetty 10

# first terminal 
./start.sh 10
# second terminal
./gradlew --rerun-tasks :loadtest:test
# fails with Terminating due to java.lang.OutOfMemoryError: Java heap space