An s3api bug that mutated statsd prefixes was previously fixed in [1].
The FakeStatsdClient subsequently introduced in [2] enables a more
targeted assertion of the statsd metric name emitted by s3api.
[1] Related-Change: Ia89485bae8f92f4f3d9f5375cab8ff08f70a11a7
[2] Related-Change: I9cdf395e85ab559c2b67b0617f898ad2d6a870d4
Change-Id: Ic2e698f3f62c2ee1f98291c4a7a4e37519471fcd