The netperf-2.7.0.tar.gz file from ftp.netperf.org is no longer
available. As a result, netperf doesn't build successfully on
the external shaker server, which causes CentOS-based Shaker
tests to fail. All netperf source and tar files have been migrated
to github. This fix changes the URL for netperf-2.7.0 to the
appropriate tar file on github. In addition, the parent directory
within the tar file has changed to "netperf-netperf-2.7.0".
A similar commit has been filed for the shaker image:
https://review.openstack.org/#/c/482177/
Change-Id: Ib7db0a0e7c5cbce7f6674b341b71aa38bbd24e24
929f2eb645