Original boot cmdline doesn't work anymore. Fixed the docs. (raspberr…

…ypi#1045)

* Original boot cmdline doesn't work anymore. 

It worked as soon as I removed init=

* Update net_tutorial.md

hardware/raspberrypi/bootmodes/net_tutorial.md

@@ -223,7 +223,7 @@ Edit /tftpboot/cmdline.txt and from `root=` onwards, and replace it with:
 root=/dev/nfs nfsroot=10.42.0.211:/nfs/client1,vers=3 rw ip=dhcp rootwait elevator=deadline
 ```
 
-You should substitute the IP address here with the IP address you have noted down.
+You should substitute the IP address here with the IP address you have noted down. Also remove any part of the command line starting with init=.
 
 Finally, edit `/nfs/client1/etc/fstab` and remove the `/dev/mmcblkp1` and `p2` lines (only `proc` should be left).