Print $ONOS_CELL when running the "onos-show-cell" command.

Change-Id: I31c627d818ae27f7a85fa16622bceae53984be98
diff --git a/tools/test/bin/onos-show-cell b/tools/test/bin/onos-show-cell
index eedea9e..5aee338 100755
--- a/tools/test/bin/onos-show-cell
+++ b/tools/test/bin/onos-show-cell
@@ -40,6 +40,7 @@
 # Load the cell setup
 . $ONOS_ROOT/tools/test/cells/${cell}
 
+echo "ONOS_CELL=${ONOS_CELL}"
 echo "ONOS_NIC=${ONOS_NIC}"
 for n in {0..9}; do
     ocn="OC${n}"