Use wf:conf('user.name') instead of userName - general framework for wf:functions

[potiuk]

We are currently using userName instead of user.name in example workflows. The user.name is used already in job.properties, and we are using userName mapping because ${user.name} is not working when workflow.xml is processed by Oozie (. in the variable name).

This can be probably replaced (and mapping removed from job.properties) with using $wf:conf('user.name') instead. From the Oozie book's TIP:

The preferred syntax for Oozie variables is ${VAR}. But this only works for variable names that follow Java naming conventions. There is another way to specify these variables and that’s by using the {wf:conf('VAR')} function. If a variable name has spaces or dots, wf:conf() is the way to go. Some users prefer this because it’s consistent with the syntax for EL functions while most users like the ${VAR} syntax because it’s simpler and also helps differentiate between variables and functions.