api: controller: Fix default out_path

ParseChroot() was supposed to use DEFAULT_OUT_PATH if no out_path was
provided in the proto; but instead, we ended up with a default Path("")
-- i.e., the current directory.

This wasn't caught by unit tests, because chroot_lib.Chroot's equality
implementation was incomplete. Fix that at the same time, as well as a
cbuildbot test that becomes exposed.

BUG=b:265885353
TEST=./run_tests

Change-Id: I3d9e1fc75b9a0ac5b8c3fa421a2035ac6a6f99b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4477624
Commit-Queue: Brian Norris <briannorris@chromium.org>
Reviewed-by: Sergey Frolov <sfrolov@google.com>
Tested-by: Brian Norris <briannorris@chromium.org>
diff --git a/api/controller/controller_util.py b/api/controller/controller_util.py
index b7da66c..07c6189 100644
--- a/api/controller/controller_util.py
+++ b/api/controller/controller_util.py
@@ -52,7 +52,11 @@
     path = chroot_message.path or constants.DEFAULT_CHROOT_PATH
     cache_dir = chroot_message.cache_dir
     chrome_root = chroot_message.chrome_dir
-    out_path = Path(chroot_message.out_path) or constants.DEFAULT_OUT_PATH
+    out_path = (
+        Path(chroot_message.out_path)
+        if chroot_message.out_path
+        else constants.DEFAULT_OUT_PATH
+    )
 
     use_flags = [u.flag for u in chroot_message.env.use_flags]
     features = [f.feature for f in chroot_message.env.features]