salt/minion.sls: set killmode=process for salt-minion,

salt/minion.sls

@@ -14,3 +14,10 @@ salt-minion:
     - source: salt://salt/files/minion.d
     # cannot clean because the salt-minion recreates /etc/salt/minion.d/_schedule.conf so it would always be unclean
     # - clean: True
+
+# deploy killmode workaround to fix broken minion upgrades
+# https://github.com/saltstack/salt/issues/7997#issuecomment-160913751
+/etc/systemd/system/salt-minion.service.d/killmode.conf:
+  file.managed:
+    - source: salt://salt/files/killmode.conf
+    - makedirs: True