qemu-config: use qemu_opts_from_qdict

qemu-config: use qemu_opts_from_qdict

Using qemu_opts_absorb_qdict, and then checking for any leftover options,
is redundant because there is already a function that does the same,
qemu_opts_from_qdict.  qemu_opts_from_qdict consumes the whole dictionary
and therefore can just return an error message if an option fails to validate.

This also fixes a bug, because the "id" entry was retrieved in
qemu_config_do_parse and then left there by qemu_opts_absorb_qdict.
As a result, it was reported as an unrecognized option.

Reported-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Fixes: 3770141139 ("qemu-config: parse configuration files to a QDict")
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>