zdtm: It's need define CLONE_NEWPID for redhat-el5

The patch allows define CLONE_NEWPID for redhat-el5 to avoid error:
test_init.c:114: error: 'CLONE_NEWPID' undeclared (first use in this function)
Signed-off-by: Victor Konyashkin  <vkonyashkin@parallels.com>
Acked-by: Andrey Wagin <avagin@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/lib/test_init.c

@@ -11,6 +11,10 @@
 #include <fcntl.h>
 
 #define STACK_SIZE	(8 * 4096)
+#ifndef CLONE_NEWPID
+/* CLONE_NEWPID since Linux 2.6.24 */
+#define CLONE_NEWPID          0x20000000
+#endif
 
 static int sig_received;
 static char dir[PATH_MAX];