Instead of malloc/free each time for DumpState, make it
static. Added DumpStatus to show status for dump.

This is to be used for detached dump.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-Id: <1455772616-8668-4-git-send-email-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>