Fix cloudlab-disksetup.sh to exit when running on non-cloudlab env

"return" makes the rest of the script executed.

Change-Id: Ifd8ac14072ef400a2bba5cd920276bac41408126
diff --git a/scripts/cloudlab-disksetup.sh b/scripts/cloudlab-disksetup.sh
index 1e2765f..b849b1c 100755
--- a/scripts/cloudlab-disksetup.sh
+++ b/scripts/cloudlab-disksetup.sh
@@ -19,7 +19,7 @@
 ###############################################
 
 # Don't do anything if not a CloudLab node
-[ ! -d /usr/local/etc/emulab ] && return
+[ ! -d /usr/local/etc/emulab ] && exit 0
 
 # Mount extra space, if haven't already
 if [ ! -d /mnt/extra ]