Don't omit execution_metadata field when empty

In CC, we have marked this field as required in the JSON schema,
which I think is correct
Add GetActualLRPsByProcessGuid to RepBBS

Signed-off-by: Max Brunsfeld <mbrunsfeld@pivotallabs.com>
Add Docker staging requests

[#75217010]

Signed-off-by: Peter Parente <pparent@us.ibm.com>
Use ExecutionMetadata in docker CC staging message

[#75217010]
Require fields in docker staging response equiv to traditional

[#75217010]