Increase Reject threshold for disabling networks

This change modifies a framework optimization. The framework optimization
disables a network when an access point repeatedly rejects requests
to associate with it. This change has some problems; one being that
it counts the rejects for all networks, and not for a specific network.
This incorrectly penalizes last networks at times; and since the current
threshold is 4 rejects, the probability of penalizing wrong networks
is high. This change ups that number to 16 to reduce that probability.

Bug: 11654725

Change-Id: I7150a9ccbb54bac44f2c2ba100fb6617ded33616