Build API: execute with --debug by default

Add the --debug flag to the reexecute function.
Also add --debug to the call scripts template.

BUG=None
TEST=manually ran endpoints.

Change-Id: I6476220f82f6c5a024f55b219e3af710d8efaffe
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2207896
Tested-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
Reviewed-by: Michael Mortensen <mmortensen@google.com>
diff --git a/api/router.py b/api/router.py
index 5d6de98..b462b6f 100644
--- a/api/router.py
+++ b/api/router.py
@@ -322,6 +322,7 @@
           chroot_output,
           config_handler.config_arg,
           chroot_config,
+          '--debug',
       ]
 
       try: