[systemtest] Properly quote executed command

Otherwise the command can't be copy-pasted into a terminal window (with
the same effect as when run through pytest).

Signed-off-by: Philipp Wagner <phw@lowrisc.org>
diff --git a/test/systemtest/utils.py b/test/systemtest/utils.py
index eb1c596..a22773b 100644
--- a/test/systemtest/utils.py
+++ b/test/systemtest/utils.py
@@ -82,7 +82,8 @@
         # the string indicating a successful startup.
         # see discussion at http://www.pixelbeat.org/programming/stdio_buffering/
         cmd = ['stdbuf', '-oL'] + self.cmd
-        self.logger.info("Running command " + ' '.join(cmd))
+        self.logger.info("Running command " +
+                         ' '.join(shlex.quote(w) for w in cmd))
 
         logfile_stdout = os.path.join(self.logdir,
                                       "{}.stdout".format(cmd_name))