cpu: Add 'ins' mode to --cpu-cap option

In this mode we test if target cpu has all features present
in image file but do not require bit to bit match: target cpu
may be a new one with more features present.

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