Changing the poll_duration parameter type to int

The poll_duration parameter is defined as a Str in config.py
but while using in code, it is converted to int. So just changing
the type in the config file, so no conversion is required when used

Change-Id: I1d10b4641e3ca8e464258857b27c450a43ad2e87
Closes-Bug:#1332283
Merge "Changing the poll_duration parameter type to int"