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_merge_to_branch.py b/scripts/cros_merge_to_branch.py
index 48e90ec..34fbc47 100644
--- a/scripts/cros_merge_to_branch.py
+++ b/scripts/cros_merge_to_branch.py
@@ -42,8 +42,8 @@
 import sys
 import tempfile
 
-from chromite.buildbot import constants
-from chromite.buildbot import repository
+from chromite.cbuildbot import constants
+from chromite.cbuildbot import repository
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib
 from chromite.lib import gerrit