clean mysql better
clean mysql better

The purge that was previously removed was actually kind of important
to burning mysql back down to a stateless zero point. Bring this back
with the addition of doing it for mariadb as well.

Change-Id: If608db8731d9ddfb2440a37387409798619b163c

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