vl: fix leak of qdict_crumple return value

vl: fix leak of qdict_crumple return value

Coverity reports that qemu_parse_config_group is returning without
unrefing the "crumpled" dictionary in case its top level item is a
list.  But actually the contract with qemu_record_config_group is
the same as for qemu_parse_config_group itself: if those function
need to stash the dictionary they get, they have to take a reference
themselves (currently this is never the case for either function).
Therefore, just add an unconditional qobject_unref(crumpled) to
qemu_parse_config_group.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>