Use openstackci/vcsrepo 0.0.8.

Version 0.0.8 of openstackci/vcsrepo fixes a bug where you could not
checkout specific git shas. This fix will allow etherpad-dev to exactly
copy the install of etherpad.o.o.

Change-Id: I55c45a4aa5acffbbfa78ca50256dbfdf6a6ebcf4
Reviewed-on: https://review.openstack.org/18826
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Tested-by: Jenkins