Updated to latest oslo-version code.

In support of tag-based versioning, update to latest oslo-version.
This changes from using versioninfo files to using PKG_INFO.

Change-Id: Ia7d212d531305997153204dfffa44beed4bad0d3
Register root_helper in test_debug_commands and test_dhcp_agent

root_helper variable currently must be introduced with a call
to register_root_helper, not with a simple assignment.

Change-Id: I3e72379925a994acfb6defb24820ab63eab43957
Fixes: bug #1117240
Merge "Updated to latest oslo-version code."