kes Fix dird/ua_cmds.c so that a cancel command checks if the

     console is authorized to cancel the job.  This fixes bug
     #767.
kes  Modify SD so that the VolCatJobs medium record is updated
     at the beginning of a Job rather than the end.  This
     fixes bug #775 where exceeding MaxVolJobs caused jobs
     to fail.
kes  Added a mutex around getting and setting Volume information
     so that multiple simultaneous jobs will single thread.