blinkpy: Remove more instances of 'LayoutTests'

Note: This CL changes the last component of LAYOUT_TEST_DIR in test.py
from 'LayoutTests' to 'wtest'.  The new name represents this directory
is related to neither 'third_party/WebKit/LayoutTests' nor
'third_party/blink/web_tests'.


Bug: 710535, 843412
Change-Id: I0529ac1b022d180d7d0779c0e19fe3d75a029de1
Reviewed-on: https://chromium-review.googlesource.com/c/1272936
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598611}
13 files changed