Fix wrong grep regular expression for tap ports
Fix wrong grep regular expression for tap ports

The regular expression used in neutron_ovs_base_cleanup omit
prefix in ovs tap ports, so wrong names are returned and used.
E.g. tap devices created for ironic in devstack are brbm-tap1
and ovs-tap1.

Change-Id: I034be6362b3d09c5296ecc413828a056712c3bd2

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