Currently, every call to avoidBadWifi fetches the current value of the config variable and setting whenever it is called. This means that the score of an unvalidated wifi network can unpredictably change at any time, creating a data race. Instead, persist the value and only update it when something changes. Bug: 31075769 Change-Id: I0f4e0e742c91ef77fabc95d3ebb494338396aca5