session03: change CLONE_STACK_SIZE from PAGE_SIZE to 4096

Update to patch "check: Introduce --ms option" (commit: 379abca9)

I find this error in my box:
cc -g -O2 -Wall -Werror -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0 -iquote ../../lib/arch/x86/include -I../../lib   session03.c ../../lib/libzdtmtst.a   -o session03
session03.c:112:7: error: variably modified ‘stack’ at file scope

The reason is :
"#define CLONE_STACK_SIZE PAGE_SIZE" is conflict with  "#define PAGE_SIZE  (sysconf(_SC_PAGESIZE))" defined in <sys/user.h>.

I think CLONE_STACK_SIZE should be seted  4096 as session02.c.

If this patch is appropriate, please let me know.
Signed-off-by: Libo Chen <libo.chen@huawei.com>
Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Acked-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/live/static/session03.c

@@ -106,7 +106,7 @@ static void mainloop()
 		handle_command();
 }
 
-#define CLONE_STACK_SIZE	PAGE_SIZE
+#define CLONE_STACK_SIZE	4096
 /* All arguments should be above stack, because it grows down */
 struct clone_args {
 	char stack[CLONE_STACK_SIZE];