As identified by Piotr in the bug mentioned below, Discover simply
returns an invalid response for any Question forwarded to it. The result
is that any update which fails to identify an update automatically will
fail due to not having payload which should be used for updating identified.

This patch fixes part of the issue, by resetting the entry for which no
payload could be identified to Updateable rather than leaving it in
limbo as Updating.

This does not fix the bug in Discover, but it does at least alleviate
the issue (it still leaves entries in Discover, rather than updating
them, but without having a way to forward that question to the user,
there's not a lot to be done about that other than output an error
message with instructions to use the GHNS dialog to do that particular
update, which of course is not exactly up to par... so, not closing the
bug with this, the issue in Discover still needs sorting out... somehow).

CCBUG:430812