private boolean dependenciesContainBlockedRole(Map<RoleCommandPair,
          Set<RoleCommandPair>> deps, Role blocked) {
    for (RoleCommandPair blockedPair : deps.keySet()) {
      if (blockedPair.getRole() == blocked) {
        return true;
      }
    }
    return false;
  }
Tests the ability to override any previous mapping by using the
{@code -OVERRIDE} placeholder. For example:

<pre>
"host_ordered_upgrade" : {
  "DATANODE-START-OVERRIDE" : ["NAMENODE-START"],
  "NODEMANAGER-START-OVERRIDE": ["RESOURCEMANAGER-START"],
  "RESOURCEMANAGER-START-OVERRIDE": ["NAMENODE-START"]
}
</pre>

@throws IOException
ambari-server/src/test/java/org/apache/ambari/server/metadata/RoleCommandOrderTest.java