Python soft IOC: Add option for updating out record without processing

It's useful to be able to update the value of an out record without having
the associated callback processing.

git-svn-id: svn+ssh://serv0002.cs.diamond.ac.uk/home/subversion/repos/controls/diamond/trunk/support/pythonSoftIoc@118673 e099a375-04f9-0310-9d5f-a741eaff62e1