Replace "dsconfigad" with SCDynamicStore call

Replace the usage of dsconfigad to determine if the machine is bound with a call to SCDynamicStore.

From a conversation with josh-miller in #Swift

let net_config = SCDynamicStoreCreate(nil, "net" as CFString, nil, nil)
    // Get Active Directory Info
    let ad_info = [ SCDynamicStoreCopyValue(net_config, "com.apple.opendirectoryd.ActiveDirectory" as CFString)]
let adDict = ad_info[0]! as! NSDictionary

let ad_path = (adDict["DomainNameDns"] as! String) + (adDict["NodeName"] as! String)

Added in build 504. Functionality should be the same, but now with less Process() work.

added Ready for Testing label

closed