jobutil: Introduce the GetUrls function.

This function will be used for getting the urls of a ddfs tag.
Make the SchemeSplit metho publicly available.
Translate the tag:// inputs into inputs usable by disco master.

The client has to get the effective inputs and send them to the master in the
jobpack.  The master then can use these inputs to schedule the tasks at the best
possible locations.
jobpack: fix two small indentation issues.
fix the location of the disco uris to include host/disco.
add a test for converting ddfs scheme for the local machine.