Fix config file generation after Glance wrapper addition
Fix config file generation after Glance wrapper addition

Commit 067af09a412a6a212a3bf77361bbfb3a9b8cc223 moved
GLANCE_BENCHMARK_OPTS to a different namespace
(rally.plugins.openstack.wrappers.glance). This broke config file
generation, since the path was not updated in common/opts.py.

Change-Id: Icde444aa27d42fd617bd9a450730480bda38c1dc

yeming233/rally,gluke77/rally,gluke77/rally,vganapath/rally,openstack/rally,vganapath/rally,eayunstack/rally,openstack/rally,amit0701/rally,eonpatapon/rally,openstack/rally,openstack/rally,eayunstack/rally,vganapath/rally,gluke77/rally,amit0701/rally,eayunstack/rally,eonpatapon/rally,vganapath/rally,amit0701/rally,yeming233/rally,gluke77/rally