Fixed docs for releasing and starting new release.
Fixed docs for releasing and starting new release.

Details:
- The Git repo is meanwhile set up such that direct pushes to
  the master branch are prohibited. This change updates the
  description on how to make a release and how to start a
  new release, to reflect that.

Signed-off-by: Andreas Maier <38dbb04957d222ea6ce72de72413b1e55e665472@de.ibm.com>

zhmcclient/python-zhmcclient,zhmcclient/python-zhmcclient