Add the new mutex that protects shared state between ram_save_live
and the iothread. If the iothread mutex has to be taken together
with the ramlist mutex, the iothread shall always be _outside_.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Umesh Deshpande <udeshpan@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com> Reviewed-by: Orit Wasserman <owasserm@redhat.com>