perf tools: Don't fail if result directory exists
perf tools: Don't fail if result directory exists

Depends-On: I23d313220607fcc8acb95ab43f55b7d9899b9b1f
Change-Id: I355a46e0b93601dc87cd65380b3aa11ae8e22140
gnocchixyz/gnocchi,leandroreox/gnocchi,gnocchixyz/gnocchi,sileht/gnocchi,sileht/gnocchi,leandroreox/gnocchi