rst: Unmap restorer dyn-args memory at the end

Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
rst: Simplify before/after remap API

Actually after remap the rst-mem is still visible in the crtools,
although at another address.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
rst: Create rst-mem pages _after_ local smaps parse

This memory is unmapped by handr, so no need in polluting
self-smaps with it.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
core: Sanitize check_core return evaluation

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>