Use deterministic command-line ordering when executing lightningd from tests

tests/utils.py

@@ -253,7 +253,7 @@ class LightningD(TailableProc):
             self.cmd_line += ['--dev-broadcast-interval=1000']
             if not random_hsm:
                 self.cmd_line += ['--dev-hsm-seed={}'.format(seed.hex())]
-        self.cmd_line += ["--{}={}".format(k, v) for k, v in LIGHTNINGD_CONFIG.items()]
+        self.cmd_line += ["--{}={}".format(k, v) for k, v in sorted(LIGHTNINGD_CONFIG.items())]
         self.prefix = 'lightningd(%d)' % (port)
 
         if not os.path.exists(lightning_dir):