com.griddynamics.jagger.agent.impl.MonitoringInfoServiceImpl#getSystemInfo needs to be refactored

[akelepko]

1. use EnumMap instead of HashMap for sysInfoStringMap.
2. split com.griddynamics.jagger.agent.model.SystemInfoCollector#getMemInfo into corresponding methods. Currently the workflow is as follows: org.hyperic.sigar.Mem gathers statistics; statistics are converted to Strings and put to a map; MonitoringInfoServiceImpl reads the map and parses the Strings into doubles, and puts into sysInfoStringMap. The intermediate conversion steps seem to be redundant.
3. you don't need to create a Thread each tome here:
   final SettableFuture<Map<String, SystemUnderTestInfo>> future = SettableFuture.create();
   jmxThreadPoolExecutor.submit(new Thread() {
   @OverRide
   public void run() {
   future.set(systemUnderTestService.getInfo());
   }
   });
   You need Callable instead.
4. why would you want to TimeUtils.sleepMillis(JMX_TIMEOUT) after timeout?
5. SystemUnderTestService statistics are collected effectively synchronously. Consider submitting the task in the beginning of the method
6. update guava dependency
7. on ExecutionException you'd rather propagate it's cause. Otherwise, there's little benefit in calling Throwables.propagate(e) as e is always checked