@Override
  public Host getHost() {
    return host;
  }
To be called during the upgrade of a specific Component in a host.
The potential upgrade states are NONE (default), PENDING, IN_PROGRESS, FAILED.
If the upgrade completes successfully, the upgradeState should be set back to NONE.
If the upgrade fails, then the user can retry to set it back into PENDING or IN_PROGRESS.
If the upgrade is aborted, then the upgradeState should be set back to NONE.

@param upgradeState  the upgrade state
ambari-server/src/main/java/org/apache/ambari/server/state/svccomphost/ServiceComponentHostImpl.java