factory_bootstrap: disable cr50-update.conf

We want to update cr50 firmware explicitly via AUTORUN or action_u in
factory_installer.sh.  Otherwise cr50 firmware might be updated
silently, and in some extreme cases, this would be an issue.

BUG=b:128049200
TEST=check dmesg, cr50-update is never run

Change-Id: Ic1e576fdb49c524b738a6275add3c505248e77f0
Reviewed-on: https://chromium-review.googlesource.com/1545815
Commit-Ready: Wei-Han Chen <stimim@chromium.org>
Tested-by: Wei-Han Chen <stimim@chromium.org>
Reviewed-by: Cheng-Han Yang <chenghan@chromium.org>
Reviewed-by: Marco Chen <marcochen@chromium.org>
diff --git a/factory_bootstrap.sh b/factory_bootstrap.sh
index bd0f0ed..b3e0ff5 100644
--- a/factory_bootstrap.sh
+++ b/factory_bootstrap.sh
@@ -52,11 +52,14 @@
   fi
 
   # Disable upstart jobs that will block execution for factory shim environment.
-  # syslog is disabled because it expects rsyslogd exists,
-  # but we don't have rsyslogd in factory shim.
+  # syslog: it expects rsyslogd exists, but we don't have rsyslogd in factory
+  #     shim.
+  # journald: it expects systemd-journald exists, which is not available in
+  #     factory shim.
+  # cr50-update: we want to update cr50 explicitly in factory_installer.sh.
   local disabled_jobs
   disabled_jobs="arc-oemcrypto powerd swap syslog tpm-probe ui update-engine
-                 journald"
+                 journald cr50-update"
 
   for job in ${disabled_jobs}; do
     file="${new_root}/etc/init/${job}.conf"