tests/qapi-schema: Demonstrate broken C code for 'if'

tests/qapi-schema: Demonstrate broken C code for 'if'

The C code generated for 'if' conditionals is incorrectly
parenthesized.  For instance,

    'if': { 'not': { 'any': [ { 'not': 'TEST_IF_EVT' },
			      { 'not': 'TEST_IF_STRUCT' } ] } } }

generates

    #if !(!defined(TEST_IF_EVT)) || (!defined(TEST_IF_STRUCT))

This is wrong.  Correct would be:

    #if !(!defined(TEST_IF_EVT) || !defined(TEST_IF_STRUCT))

Cover the issue in qapi-schema-test.json.  This generates bad #if in
tests/test-qapi-events.h and other files.

Add a similar condition to doc-good.json.  The generated documentation
is fine.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210831123809.1107782-5-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>