[FaceRestTestUtils] Remove the DB setting in the helper function.

Calling a DB setup function in the middle much degrades readability
and may cause unexpected behaivor.

startFaceRest() still have a similar line that calls defineDBPath().
I will also remove this later.
Merge pull request #462 from project-hatohol/cleanup-face-rest-test-util

[FaceRestTestUtils] Remove the DB setting in the helper function.