Corrects the class name "ExtensionManager"

Corrects ExtensionManager to extensions.ExtensionManager which was
earlier written without the package name.

There were no errors encountered as first condition of the condition set
always evaluated True.

Change-Id: I1fd4016105a99a7baaad6d2613b0e709a09aeeb2
Closes-Bug: #1323400
Clean up openstack-common.conf

The issues are detected by new change about update.py
in I68c0108304be8a315bcefe939c22019caab9bc98. This patch
doesn't depend the oslo-incubator patch.
 * remove unused module config
 * add missing module loopingcall and remove module
   cfg in openstack-common.conf
 * sort the modules in openstack-common.conf

Closes-Bug: #1323622
Change-Id: I10cca7386ea8e586f7e35a2f0e5b3c5c14906d7e
Merge "Corrects the class name "ExtensionManager""
Merge "Clean up openstack-common.conf"