Pre-split cat step.yml command

We are passing the command as an array, so we need to pre-split the
command into separate words.

buildbot/master/files/config/factories.py

@@ -130,9 +130,8 @@ def __init__(self, builder_name, environment, yaml_path, **kwargs):
     @defer.inlineCallbacks
     def run(self):
         try:
-            print_yaml_cmd = "cat {}".format(self.yaml_path)
             cmd = yield self.makeRemoteShellCommand(
-                command=[print_yaml_cmd],
+                command=["cat", "./{}".format(self.yaml_path)],
                 collectStdout=True
             )
             yield self.runCommand(cmd)