Report last boot reason if userspace reboot fails

Will help in debugging failing tests

Test: atest CtsUserspaceRebootHostSideTestCases
Bug: 149020865
Change-Id: I59ff04c7921c628eeb1fad73bacdd4b74677bc04
diff --git a/PREUPLOAD.cfg b/PREUPLOAD.cfg
index 39a0f35..3eb8458 100644
--- a/PREUPLOAD.cfg
+++ b/PREUPLOAD.cfg
@@ -34,6 +34,7 @@
                       tests/tests/widget/
                       common/device-side/util/
                       hostsidetests/stagedinstall/
+                      hostsidetests/userspacereboot/
                       tests/tests/packageinstaller/atomicinstall/
 
 ktlint_hook = ${REPO_ROOT}/prebuilts/ktlint/ktlint.py -f ${PREUPLOAD_FILES}