Increase test stability again.

test/tests/openwrt_docker_test.py

@@ -107,8 +107,15 @@ def run_openwrt_shell_command(command, *arg):
     if process.stdout == "":
         return None
 
+    # Sometime it happens that also the previous command return is included which results in two or more json strings.
+    jsons = process.stdout.split('\n')
+
+    # Search for 'return' and give back the last occurrence index
+    idx = next((i for i, s in reversed(list(enumerate(jsons))) if 'return' in s), -1)
+
     # Assume json here, parse it
-    ret = json.loads(process.stdout)
+    ret = json.loads(jsons[idx])
+
     data = ret['return']
 
     # decode output