action-scripts: Add "pre-resume" stage

The main idea is to be able to operate with container
at the moment where its processess and resources are
already restored but the processes are not yet in
running state, ie just before we kick them.

Beside the need of tuning up beancounters (which is vz7
specific feature) this might be useful to make some
additional debug tests from the script.

We can't reuse ACT_POST_RESTORE action or move it because
we can kill the restored processes here and resume them
on a source side as avagin@ explained.

[ xemul: In between POST_RESTORE and PRE_RESUME ghost files
  are cleaned up (an a little bit more), so two separate
  stages are required and the latter one cannot fail. ]

travis-ci: success for Add "pre-resume" stage
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>