[DWRF] Remove redundant stuff from TestFileDump

Summary:
@public
We already create conf object in @Before which is invoked before *every* individual test case so no need to have multiple objects

Test Plan: ran test cases

Reviewers: kevinwilfong

Reviewed By: kevinwilfong

Subscribers: hive-devel@

Differential Revision: https://phabricator.fb.com/D1450904

Tasks: 4738072