In commit 97cfb707 we extended scm_fdset structure
up to 7K thus we need to increase the parasite stack
size enough to hold it. It was not noticed simply because
we were poking arguments area of memory.

The memory map of args and stack for parasite look like

  +-----------+   min address
  |           | |
  | arguments | v (8K)
  |           |
  +-----------+
  |           |
  |   stack   | ^ (16K)
  |           | |
  +-----------+   max address
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>