[NET]: Fix permissions of /proc/net

commit e9720acd ([NET]: Make /proc/net a symlink on /proc/self/net (v3))
broke ganglia and probably other applications that read /proc/net/dev.

This is due to the change of permissions of /proc/net that was
introduced in that commit.

Before: dr-xr-xr-x 5 root root 0 Mar 19 11:30 /proc/net
After: dr-xr--r-- 5 root root 0 Mar 19 11:29 /proc/self/net

This patch restores the permissions to the old value which makes
ganglia happy again.

Pavel Emelyanov says:

	This also broke the postfix, as it was reported in bug #10286
	and described in detail by Benjamin.
Signed-off-by: Andre Noll <maan@systemlinux.org>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

fs/proc/base.c

@@ -2270,7 +2270,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	DIR("fd",         S_IRUSR|S_IXUSR, fd),
 	DIR("fdinfo",     S_IRUSR|S_IXUSR, fdinfo),
 #ifdef CONFIG_NET
-	DIR("net",        S_IRUGO|S_IXUSR, net),
+	DIR("net",        S_IRUGO|S_IXUGO, net),
 #endif
 	REG("environ",    S_IRUSR, environ),
 	INF("auxv",       S_IRUSR, pid_auxv),