qapi: Consolidate QMP input visitor creation

qapi: Consolidate QMP input visitor creation

Rather than having two separate ways to create a QMP input
visitor, where the safer approach has the more verbose name,
it is better to consolidate things into a single function
where the caller must explicitly choose whether to be strict
or to ignore excess input.  This patch is the strictly
mechanical conversion; the next patch will then audit which
uses can be made stricter.

Signed-off-by: Eric Blake <[email protected]>
Message-Id: <1461879932[email protected]>
Signed-off-by: Markus Armbruster <[email protected]>