IPython: make $ipythondir writable for IPython user

* Remove operating system check.
* Remove defined() checks; this doesn't really work because if another
  declaration exists, and that declaration is not wrapepd with a defined()
  check, and it happens to be instantiated before this one, you get a duplicate
  resource definition error.
* Don't set ipython user's home directory to $ipythondir. No reason to.
* Re-tab. (Yes, mixing formatting / behavior changes in a single patch, sorry.)

Change-Id: I933b57a530fdc437c80eaad5970d66840faa8cbc
Merge "IPython: make $ipythondir writable for IPython user" into production