Job adding has issues handling form after validation issues

[adambray]

Multiple things go wrong if a job add form is submitted and doesn't pass
validation. None of them are too important though

• if "compute hours" is selected,
• defaults to "input hours" option
• defaults to times from url
• the time interval is added in parenthesis to the description text
  box. This means the next submit adds another set of times, and repeats.
  Giving us entries like "(02:30PM to 02:30PM) (02:30PM to 02:30PM)
  (02:26PM to 02:26PM) test" in the job
• empty description still works since time parens are added