When we're freezing processes we don't count on anything but
rather do 5 attempts with constantly increasing delay.

Lets rather do the following:

 - take --timeout option into account (which is 5 seconds
   by default) and split it into 100 ms steps;

 - when frezing processes check freezer status every 100 ms.

Same time it looks that 5 seconds by default is too small
for high loaded containers. Lets increase it to 10 seconds
by default.

[ skinsbursky@:
Frankly speaking, in this particular case increasing intervals are not nice.
This is not a network issue or something.
Usually freezing takes less than a second, but more, that, say 200ms.
Otherwise it takes quite o lot of time.
If step size is growing all the time, in most of the cases criu will
waste hundreds of milliseconds between iterX (say, third) and (iterX+1)
because of the growing step size.
100ms step looks solid enough: not to small to produce a lot of syscalls
and not to large to waste a lot of time.
With previous scheme freezing was usually taking half a second more that
it should because of this growing step.

[ gorcunov@:
You won't belive, but been able to sepcify --timeout 0 here allowed
me and Stas to catch serieous problem in freezer code.

https://lkml.org/lkml/2016/8/3/317

Without this feature we would have to patch criu instead. So you know,
this would be great to keep it for catching more kernel bugs ;)
Reported-by: Stanislav Kinsburskiy <skinsbursky@virtuozzo.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>