configure: Fix --without-default-features propagation to meson

A typo prevents that many features get disabled when the user
runs "configure" with the --without-default-features switch.

Reported-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20210713093155.677589-2-thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>