Comment 0 for bug 1726422

Ike version V1 divides two phases to create ike&ipsec tunnel,the ike_phase1_mode(main mode or aggresive mode) is used in first phase to negotiate ike tunnel.
Ike version v2 create ipsec sa in only one phase. If ike policy uses ike V2,it will be unnecessary to use ike_phase1_mode.
Now the ike_phase1_mode only support main mode,it cannot be modified to set null,it need be extended to support,like ike_phase1_mode:["main",null].