Re-Add default db connection string
Re-Add default db connection string

When latest db code from oslo was synced, the default connection string
was removed and the db option groups were mereged into one group. This
patch sets the default connection string oustide the olso db code in
clutuils.run.

Change-Id: Ia73767e05b6411c8f57f421d6262f85c0e5c99cb
Closes-Bug: #1302570

ytsarev/rally,vponomaryov/rally,yeming233/rally,gluke77/rally,group-policy/rally,vganapath/rally,varunarya10/rally,paboldin/rally,afaheem88/rally,gluke77/rally,cernops/rally,go-bears/rally,cernops/rally,vefimova/rally,paboldin/rally,redhat-openstack/rally,go-bears/rally,openstack/rally,eayunstack/rally,aplanas/rally,amit0701/rally,group-policy/rally,openstack/rally,vganapath/rally,amit0701/rally,aforalee/RRally,group-policy/rally,shdowofdeath/rally,paboldin/rally,varunarya10/rally,eayunstack/rally,pyKun/rally,aplanas/rally,pyKun/rally,gluke77/rally,eonpatapon/rally,redhat-openstack/rally,ytsarev/rally,eayunstack/rally,aforalee/RRally,pandeyop/rally,amit0701/rally,vganapath/rally,afaheem88/rally,vponomaryov/rally,gluke77/rally,yeming233/rally,pandeyop/rally,eonpatapon/rally,vefimova/rally,vganapath/rally,shdowofdeath/rally,openstack/rally,openstack/rally