fix: tgtd mount propagation

With #411 `/proc` mounts were dropped, but we need to set proper mount
propagation, otherwise shutdown hangs for a long time.

Signed-off-by: Noel Georgi <git@frezbo.dev>

storage/iscsi-tools/tgtd.yaml

@@ -7,6 +7,8 @@ depends:
        - hostname
        - etcfiles
 container:
+  security:
+    rootfsPropagation: shared
   entrypoint: /usr/local/sbin/tgtd
   args:
     - -f