pr_manager_worker() passes its @opaque argument to g_free().  Wrong;
it points to pr_manager_worker()'s automatic @data.  Broken when
commit 2f3a7ab3 converted @data from heap- to stack-allocated.  Fix
by deleting the g_free().

Fixes: 2f3a7ab3
Cc: qemu-stable@nongnu.org
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>