Fix issues syncing sample generator in update.py

When updating the openstack.common.config module, the shutil module
raises an exception when attemting to copy a directory.
Fixed to skip directories as copy targets and handle directories
of target module names.
Fixed problem of wrong import path of the generator module.

Change-Id: Ie8336b070573c74691ab5e7304dd05c540826c53
Merge "Fix issues syncing sample generator in update.py"