Change naming of constants in test.env.paths. (FACTORY_DIR)

This change the naming of constants in test.env.paths for directories
/usr/local/factory/*, according to go/GoofyFHS.

Changes:
* FACTORY_PATH -> FACTORY_DIR
* FACTORY_PACKAGE_PATH -> FACTORY_PYTHON_PACKAGE_DIR
* FIRMWARE_UPDATER_PATH -> FACTORY_FIRMWARE_UPDATER_PATH

BUG=None
TEST=make test

Change-Id: I9b505c788d0f75d2b930c40cc4e7b16aad31260e
Reviewed-on: https://chromium-review.googlesource.com/518604
Commit-Ready: Pi-Hsun Shih <pihsun@chromium.org>
Tested-by: Pi-Hsun Shih <pihsun@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
diff --git a/py/gooftool/commands.py b/py/gooftool/commands.py
index 36b1cd0..b7c6b9d 100755
--- a/py/gooftool/commands.py
+++ b/py/gooftool/commands.py
@@ -559,7 +559,7 @@
   else:
     event_log.Log(
         'source_hashes',
-        **file_utils.HashSourceTree(os.path.join(paths.FACTORY_PATH, 'py')))
+        **file_utils.HashSourceTree(os.path.join(paths.FACTORY_DIR, 'py')))
 
 
 @Command('log_system_details')