get_of_rules corrected

Change-Id: I4b3d6d2f035765f595b797320d8f42d7dddac09f
Signed-off-by: garciaana <naiara.garciaa@ehu.eus>
diff --git a/onos.py b/onos.py
index 53def9d..86fbac7 100644
--- a/onos.py
+++ b/onos.py
@@ -212,6 +212,7 @@
                 return r, c
         # get rules
         try:
+	    self.headers['content-type'] = 'text/plain'
             of_response = requests.get(self.url + "flows/" + self.id, headers=self.headers)
             error_text = "Openflow response %d: %s" % (of_response.status_code, of_response.text)