simple-init: Swap continue for true

Continue is not valid, and in the current syntax usage for 80-simple-init,
the error is logged. Swapped to true to act as a no-op.

/tmp/in_target.d/post-install.d/80-simple-init: line 30: continue: \
    only meaningful in a `for', `while', or `until' loop

Change-Id: I9ddb9aadc1114c0f4dea14d31b9751d83a887a6b

diskimage_builder/elements/simple-init/post-install.d/80-simple-init

@@ -27,7 +27,7 @@ case "$DIB_INIT_SYSTEM" in
         else
             # NOTE(ianw): it might be better to whitelist platforms in
             # the future, but for now assume it will "just work"
-            continue
+            true 
         fi
         ;;
     openrc)