secrets.get should return a list

The secrets.get function may return more than 1 secret, such as when using the '.../secrets/' API without specifying a particular UUID.  The 'secrets.get' function currently barfs when it gets a list of secrets back because it always assumes it is getting just 1 and not a list.

This fix changes secrets.get to always return a list, even if its just a list of 1.  This also updates the 'keep' client to handle the result as a list instead of as a single object.