dump: Make sure we're dumping task not running in compat mode

It's been reported that we do not test if the tracee is 32bit
task running kn 64bit kernel. This patch adds such test.

https://bugzilla.openvz.org/show_bug.cgi?id=2505



Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>