Integration tests should try to kill the server before trying to start it

Some integration tests use an Ant file to start one or more external servers and then kill them. Sometimes the kill step doesn't run, e.g. in this example the JVM died with an internal error:

http://ci.infinispan.org/viewLog.html?buildId=50891&buildTypeId=bt9&tab=buildResultsDiv

The server then stayed up and caused lots of failures in the test suite runs that followed, apparently without the kill step running in any of those runs. We should add a kill step before trying to start the server.