Bug 6987

The following cluster document results in failure to contextualize and an error
on the context broker.

<cluster xmlns="http://www.globus.org/2008/06/workspace/metadata/logistics">
  <workspace>
    <name>head-node</name>
    <image>lenny-vm.raw.gz</image>
    <quantity>1</quantity>
    <nic wantlogin="true">public</nic>
    <ctx>
      <provides>
    <identity />
    <role>head-node</role>
      </provides>
      <requires>
    <identity />
    <role name="compute-node" hostname="true" pubkey="true" />
      </requires>
    </ctx>
  </workspace>

  <workspace>
    <name>compute-nodes</name>
    <image>lenny-vm.raw.gz</image>
    <quantity>1</quantity>
    <nic>public</nic>
    <ctx>
      <provides>
        <identity />
        <role>compute-node</role>
      </provides>
    </ctx>
  </workspace>
</cluster>

The error on broker log is:
"Blackboard is not aware of node with ID #13"

After adding an empty requires block to the compute-nodes ctx block, it works.