parasite: Increase stack size up to 16K

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>

include/parasite.h

 #ifndef CR_PARASITE_H_
 #define CR_PARASITE_H_
 
-#define PARASITE_STACK_SIZE	2048
+#define PARASITE_STACK_SIZE	(16 << 10)
 #define PARASITE_ARG_SIZE	8196
 
 #define PARASITE_MAX_SIZE	(64 << 10)