Use authentication when fetching artifacts from the LAVA master

If the LAVA device has security permissions, we will need to use
authentication for fetching artifacts. Since we already have the
username and token, use those.

Change-Id: Iace02986cbd73a650693eaa2aff66ac389f8e26c
diff --git a/tfm_ci_pylib/lava_rpc_connector.py b/tfm_ci_pylib/lava_rpc_connector.py
index 8edd322..9bab0e5 100644
--- a/tfm_ci_pylib/lava_rpc_connector.py
+++ b/tfm_ci_pylib/lava_rpc_connector.py
@@ -56,6 +56,8 @@
 
         self.server_job_prefix = "%s/scheduler/job/%%s" % self.server_url
         self.server_results_prefix = "%s/results/%%s" % self.server_url
+        self.token = token
+        self.username = username
         super(LAVA_RPC_connector, self).__init__(server_addr)
 
     def _rpc_cmd_raw(self, cmd, params=None):
@@ -71,8 +73,12 @@
         print("\n".join(self.system.listMethods()))
 
     def fetch_file(self, url, out_file):
+        auth_params = {
+            'user': self.username,
+            'token': self.token
+        }
         try:
-            with requests.get(url, stream=True) as r:
+            with requests.get(url, stream=True, params=auth_params) as r:
                 with open(out_file, 'wb') as f:
                     shutil.copyfileobj(r.raw, f)
             return(out_file)