support: check SITE/IFO vars in module wrapper script

support/bin/rts_module_ctrl

@@ -3,9 +3,17 @@
 cmd="$1"
 sys="$2"
 if [ -z "$sys" ] ; then
-    echo "usage: $(basename $0) start|stop <sys>"
+    echo "usage: $(basename $0) start|stop <sys>" >&2
     exit 1
 fi
+if [ -z "$SITE" ] ; then
+    echo "SITE variable not specified." >&2
+    exit 2
+fi
+if [ -z "$IFO" ] ; then
+    echo "IFO variable not specified." >&2
+    exit 2
+fi
 TARGET=/opt/rtcds/${SITE,,*}/${IFO,,*}
 case $cmd in
     start)