lsof check is too expensive

ISPN-12280 added a test run of lsof infinispan-server.xml, to ensure that it exists before trying to start the server and finding out that we can't kill it. Unfortunately, the test run is without any arguments, so the command execution takes a long time and lists all the open files in the system and put them in a system property.

On my system, the output of lsof is 86MB, and now I can't run mvn -X with -Xmx512m any more.