Fix corrupted list after reverse shutdown client traversal

Fix corrupted list after reverse shutdown client traversal

The problem is that g_list_reverse() modifies the list in place, so in
order to not corrupt the shutdown client list of the NSMConsumerService,
we would have to copy the list. What this commit does instead is to not
call g_list_reverse() and instead traverse the list in reverse order
directly.

This commit also improves the shutdown logging a bit.