Cleanup openstack-common.conf

The file contained modules from oslo-incubator that don't exist, never
existed, have graduated to oslo, are not used or are not directly used
(used only as dep for a module directly used by savanna)

With this commit the file will contain only modules that are directly
used by savanna

Also, all oslo-incubator sync'd code for unused modules has been
removed

Details -

 * config is now in oslo, need config.generator for generate_sample.sh
 * context is not used directly by savanna, used via db.sqlalchemy
 * gettextutils is not used directly by savanna, used via multiple
   other modules
 * local is not used directly by savanna, used via log
 * loopingcall is not used directly by savanna, used via threadgroup
 * py3kcompat no longer exists, it is removed
 * service is not used by savanna or any deps, it is removed
 * setup does not exist
 * thread_group does not exist
 * version does not exist
 * versionutils is not used, it is removed
 * excess comments removed

Implements: blueprint cleanup-savanna-openstack-common.conf
Change-Id: I05903a7a551b6f88b2e78c4dae2d02362aae1fbd
Merge "Cleanup openstack-common.conf"