[hotfix] Set number of Mesos agent CPUs to 8

This commits sets the number of CPUs on a Mesos agent to 8 which is the same
as the number assigned vcores to a NodeManager in the Yarn case. This allows
to spawn 3 Mesos tasks on an agent if there is enough memory. This will give
us the same number of TMs possible as in the Yarn case.

flink-jepsen/src/jepsen/flink/mesos.clj

@@ -68,7 +68,8 @@
  (str "--log_dir=" log-dir)
  (str "--master=" (zookeeper-uri test zk-namespace))
  (str "--recovery_timeout=30secs")
- (str "--work_dir=" slave-dir)]))
+ (str "--work_dir=" slave-dir)
+ (str "--resources='cpus:8'")]))
 
 (defn create-mesos-master-supervised-service!
  [test node]