Rename chromite.buildbot -> chromite.cbuildbot.

The cbuildbot script lives in a directory named buildbot. Which is a
bit confusing.

BUG=chromium:373277
TEST=Unitests + cros lint.
CQ-DEPEND=CL:200157
CQ-DEPEND=CL:200165
CQ-DEPEND=CL:200149
CQ-DEPEND=CL:*163598
CQ-DEPEND=CL:*163760
CQ-DEPEND=CL:*163786

Change-Id: Ia5953a4506e8b47d27e1a6908ecb938a439da8c2
Reviewed-on: https://chromium-review.googlesource.com/199664
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
diff --git a/scripts/cros_generate_sysroot.py b/scripts/cros_generate_sysroot.py
index 07b764d..ceece45 100644
--- a/scripts/cros_generate_sysroot.py
+++ b/scripts/cros_generate_sysroot.py
@@ -10,7 +10,7 @@
 
 import os
 
-from chromite.buildbot import constants
+from chromite.cbuildbot import constants
 from chromite.lib import cros_build_lib
 from chromite.lib import commandline
 from chromite.lib import osutils