P2P: Set station disconnected state scan interval when P2P connected

When P2P is in connected state, and station is in disconnected state,
framework issues SCAN with an interval which shall be configured using
global flag WIFI_SCAN_INTERVAL_WHEN_P2P_CONNECTED_MS. Set this flag
default to three minutes, to improve throughput.

Change-Id: I95a937d74da222432c73462657e4e97473bb6532
CRs-Fixed: 901633