Job submission can take a long time during Cluster initialization

During initialization in Cluster.java, the framework provider classes are loaded inside a sync block which can considerably increase job submission time when the number of submissions are high. The motive is to reduce time spent in this sync block safely to improve performance.

synchronized (frameworkLoader) {
      for (ClientProtocolProvider provider : frameworkLoader) {
        LOG.debug("Trying ClientProtocolProvider : "
            + provider.getClass().getName());