api: controller/sysroot.py: Use workon flag

BUG=b:276310194
TEST=CQ

Change-Id: Ie1c26082b6d280ed0e33c585850f556fa53bfe29
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4385954
Tested-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/api/controller/sysroot_unittest.py b/api/controller/sysroot_unittest.py
index 6d75e5d..5f1a84f 100644
--- a/api/controller/sysroot_unittest.py
+++ b/api/controller/sysroot_unittest.py
@@ -852,6 +852,7 @@
             incremental_build=False,
             dryrun=False,
             backtrack=sysroot_controller.DEFAULT_BACKTRACK,
+            workon=False,
         )
 
     def testSuccessWithGomaLogs(self):