carbonara: fix benchmark output now that compression is out
carbonara: fix benchmark output now that compression is out

Just indicate the serialization speed.

Closes-Bug: #1611089
Change-Id: I2326f1f036a93d713b023dfcfaab86b6f42673b7

sileht/gnocchi,leandroreox/gnocchi,leandroreox/gnocchi,gnocchixyz/gnocchi,gnocchixyz/gnocchi,sileht/gnocchi