fix regression test

Summary: as title

Test Plan: push

Reviewers: igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D18999
give correct metric name for grep in regression script

Summary: as title

Test Plan: jenkin

Reviewers: igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19005