qapi: don't pass two copies of TestInputVisitorData to tests

qapi: don't pass two copies of TestInputVisitorData to tests

The input_visitor_test_add() method was accepting an instance
of 'TestInputVisitorData' and passing it as the 'user_data'
parameter to test functions. The main 'TestInputVisitorData'
instance that was actually used, was meanwhile being allocated
automatically by the test framework fixture setup.

The 'user_data' parameter is going to be needed for tests
added in later patches, so getting rid of the current mistaken
usage now allows this.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1475246744-29302-7-git-send-email-berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>