Enhance group handling in extract_opts

When there's 2 options with the same name, the script gets confused and
doesn't know in which group it goes. This fixes it, and fixes also the
template generation which is broken for various reasons:

- gettext.install was missing
- nova-rootwrap when imported calls exit() because it doesn't find a valid
  configuration file, so let's exclude it entirely anyway
- eventlet/greendns needs to be ignored for this

Change-Id: Iaa4e9a806e79032ce1675b46a6b7a7628c3eff89
Signed-off-by: Julien Danjou <julien@danjou.info>
Merge "Enhance group handling in extract_opts"