Improve performance of api requests with hbase scan
Improve performance of api requests with hbase scan

Added columns argument to hbase scan requests, it allows to
reduce response size. With this patch we get only required for
filtering cells of scanned rows.

Change-Id: I2c15276965db1dec6a0e9f595ee7c83b33e4cff2

openstack/ceilometer,fabian4/ceilometer,openstack/ceilometer,ityaptin/ceilometer,MisterPup/Ceilometer-Juno-Extension,redhat-openstack/ceilometer,eayunstack/ceilometer,openstack/aodh,MisterPup/Ceilometer-Juno-Extension,r-mibu/ceilometer,m1093782566/openstack_org_ceilometer,eayunstack/ceilometer,sileht/aodh,redhat-openstack/ceilometer,idegtiarov/ceilometer,cernops/ceilometer,Juniper/ceilometer,cernops/ceilometer,openstack/aodh,chungg/aodh,maestro-hybrid-cloud/ceilometer,pczerkas/aodh,idegtiarov/ceilometer,pczerkas/aodh,luogangyi/Ceilometer-oVirt,froyobin/ceilometer,sileht/aodh,chungg/aodh,fabian4/ceilometer,mathslinux/ceilometer,pkilambi/ceilometer,isyippee/ceilometer,m1093782566/openstack_org_ceilometer,luogangyi/Ceilometer-oVirt,froyobin/ceilometer,r-mibu/ceilometer,ityaptin/ceilometer,isyippee/ceilometer,Juniper/ceilometer,mathslinux/ceilometer,pkilambi/ceilometer,maestro-hybrid-cloud/ceilometer