tools/kvm_stat: print 'Total' line for multiple events only

The 'Total' line looks a bit weird when we have a single event only. This
can happen e.g. due to filters. Therefore suppress when there's only a
single event in the output.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>