In e06484b0f4, we added specific
handling for outbound-channel initial monitor updates failing -
in such a case we have a counterparty who tried to open a second
channel with the same funding info we just gave them, causing us
to force-close our outbound channel as it shows up as
duplicate-funding. Its largely harmless as it leads to a spurious
force-closure of a channel with a peer doing something absurd,
however it causes the `full_stack_target` fuzzer to fail.
Sadly, in 574c77e7bc, as we were
dropping handling of `PermanentFailure` handling for updates, we
accidentally dropped handling for initial updates as well.
Here we fix the issue (again) and add a test.
7bc2a148b2