controller.py/service.py: Add and use the --force with Delete endpoint.

BUG=chromium:1095661
TEST=manual, run_tests

Change-Id: I1d2118222ae6f86607304ad24705c72abed97543
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2278108
Commit-Queue: Michael Mortensen <mmortensen@google.com>
Tested-by: Michael Mortensen <mmortensen@google.com>
Reviewed-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/api/controller/sdk.py b/api/controller/sdk.py
index dac9388..ccf3ee6 100644
--- a/api/controller/sdk.py
+++ b/api/controller/sdk.py
@@ -101,7 +101,7 @@
 def Delete(input_proto, _output_proto, _config):
   """Delete a chroot."""
   chroot = controller_util.ParseChroot(input_proto.chroot)
-  sdk.Delete(chroot)
+  sdk.Delete(chroot, force=True)
 
 
 @faux.all_empty