fix(#304): wait a bit more when killing scylla-jmx on timeout

The `SIGQUIT` is follow too soon by a forcefull kill, i.e. we don't let
the process enough time to print the output to stdout

Close: #303
Ref: scylladb/scylladb#7991 (comment)

ccmlib/scylla_node.py

@@ -660,6 +660,7 @@ def nodetool(self, *args, **kwargs):
         except subprocess.TimeoutExpired:
             self.error("nodetool timeout, going to kill scylla-jmx with SIGQUIT")
             self.kill_jmx(signal.SIGQUIT)
+            time.sleep(5)  # give the java process time to print the threaddump into the log
             raise
 
     def kill_jmx(self, __signal):