Fixed opportunistic key caching (OKC)
wpa_sm_set_config() can be called even if the network block does not
change. However, the previous version ended up calling
pmksa_cache_notify_reconfig() every time and this cleared the network
context from PMKSA cache entries. This prevented OKC from ever being used.
Do not call pmksa_cache_notify_reconfig() if the network context remains
unchanged to allow OKC to be used.