vty: Check the result of the write command

When running on top of vboxsf the write option doesn't work and we
have a success that should be a failure. Check the success string
we want to see on write.

Change-Id: I460e2da10f049807e4729f53fc69448c9c30f5f9

osmopy/osmotestconfig.py

@@ -94,7 +94,9 @@ def copy_config(dirname, config):
 
 def write_config(vty):
     new_config = vty.enabled_command("write")
-    print new_config.split(' ')[-1]
+    if not new_config.startswith("Configuration saved to "):
+        print(new_config)
+        return 1, [new_config]
     return 0