Add copyright text to openstack/common/__init__.py

The copyright text was remove from the file and as it now contains
code, it is missing. This patch readds the copyright text and also
fixes formatting, as adds empty lines between the import and the first
line of code.

Closes-bug: #1288877

Change-Id: I37013194cc808d919ff2345099cd1d053ffe7d88
Merge "Add copyright text to openstack/common/__init__.py"