external test scripts: Quote variables properly

scripts/common.sh

@@ -37,21 +37,21 @@ safe_kill()
     local n=1
 
     # only proceed if $PID does exist
-    kill -0 $PID 2>/dev/null || return
+    kill -0 "$PID" 2>/dev/null || return
 
     echo "Sending SIGTERM to ${NAME} (${PID}) ..."
-    kill $PID
+    kill "$PID"
 
     # wait until process terminated gracefully
-    while kill -0 $PID 2>/dev/null && [[ $n -le 4 ]]; do
+    while kill -0 "$PID" 2>/dev/null && [[ $n -le 4 ]]; do
         echo "Waiting ($n) ..."
         sleep 1
         n=$[n + 1]
     done
 
     # process still alive? then hard-kill
-    if kill -0 $PID 2>/dev/null; then
+    if kill -0 "$PID" 2>/dev/null; then
         echo "Sending SIGKILL to ${NAME} (${PID}) ..."
-        kill -9 $PID
+        kill -9 "$PID"
     fi
 }