gnocchi: fixes the instance flavor type
gnocchi: fixes the instance flavor type

In nova the instance flavor id can be a uuid since a while now.

This change removes the asssumption that it's a integer.

Change-Id: I8b2428c943cc264e258815035379a444c61cbe8f

openstack/ceilometer,mathslinux/ceilometer,fabian4/ceilometer,redhat-openstack/ceilometer,r-mibu/ceilometer,isyippee/ceilometer,idegtiarov/ceilometer,ityaptin/ceilometer,cernops/ceilometer,r-mibu/ceilometer,mathslinux/ceilometer,maestro-hybrid-cloud/ceilometer,isyippee/ceilometer,redhat-openstack/ceilometer,cernops/ceilometer,eayunstack/ceilometer,fabian4/ceilometer,ityaptin/ceilometer,eayunstack/ceilometer,openstack/ceilometer,maestro-hybrid-cloud/ceilometer,idegtiarov/ceilometer