switch to use ceilometer specific connections
switch to use ceilometer specific connections

in Juno/Kilo, we added ceilometer purpose specific connections for:
metering, alarms, event. Rather than piggyback off oslo.db's
connection option (which gives misleading sql help message), we
should use Ceilometer specific connections.

Change-Id: I7703b73708a5807fb8de89fbb828f06b488acf69

bljgaurav/openstack-test,olivierlemasle/devstack,mmasaki/devstack,bswartz/devstack,NaokiMiyata/devstack,parul24/devstack,vsham20/devstack,andrewrothstein/devstack,kplus/devstack-moonshot,ozamiatin/devstack,Mahito/devstack,BSJAIN92/OpenStack,TwinkleChawla/devstack,BSJAIN92/OpenStack,liuquansheng47/devstack,liuquansheng47/devstack,pombredanne/devstack,herrsechs/devstack,vishnugonela/devstack,HPCHub/devstack,flavio-fernandes/devstack,samgoon/devstack,openstack-dev/devstack,bljgaurav/openstack-test,promptworks/devstack,j4/devstack,samgoon/devstack,flavio-fernandes/devstack,bq-xiao/devstack,prithivm/branch01,neerja28/Devstack_GlusterFS,sc68cal/devstack,nuxeh/devstack,Mahito/devstack,CloudServer/devstack,eharney/devstack,vsham20/devstack,wenhuizhang/devstack,sequenceiq/devstack,eharney/devstack,andrewrothstein/devstack,herrsechs/devstack,dirkmueller/devstack,dirkmueller/devstack,upadhyay-prashant/devstack,CloudServer/devstack,dtroyer/devstack,pombredanne/devstack,mc2014/devstack,bigswitch/devstack,LoHChina/devstack,vishnugonela/devstack,NaokiMiyata/devstack,mmasaki/devstack,nawawi/openstack,sequenceiq/devstack,nuxeh/devstack,bigswitch/devstack,pczerkas/devstack,varunarya10/devstack,affo/devstack,openstack-dev/devstack,pacinete/devstack,noironetworks/devstack,wenhuizhang/devstack,rushiagr/devstack,parul24/devstack,j4/devstack,mc2014/devstack,richliu/devstack,pczerkas/devstack,bswartz/devstack,LoHChina/devstack,dtroyer/devstack,neerja28/Devstack_GlusterFS,ozamiatin/devstack,costingalan/devstack,avvocatodemarchis/devstack,affo/devstack,prithivm/branch01,mssumanth/devstack,pacinete/devstack,noironetworks/devstack,thomasem/devstack,kplus/devstack-moonshot,bq-xiao/devstack,olivierlemasle/devstack,rushiagr/devstack,atulpatil301/devstack,upadhyay-prashant/devstack,TwinkleChawla/devstack,avvocatodemarchis/devstack,costingalan/devstack,promptworks/devstack,mssumanth/devstack,group-policy/devstack,sc68cal/devstack,atulpatil301/devstack,richliu/devstack,nawawi/openstack,group-policy/devstack,thomasem/devstack,varunarya10/devstack,HPCHub/devstack