config+itest: allow unsafe disconnect by default

This commit beings the process of deprecating unsafe-disconnect. Many
moons ago this was disallowed to prevent concurency bugs surrounding
reconnect. Despite the name, it has been safe to enable this feature for
well over a year, as several PRs have been merged that addressed the
possible issues that existed when the feature was added.

config.go

@@ -271,7 +271,7 @@ type config struct {
 
 	Profile string `long:"profile" description:"Enable HTTP profiling on given port -- NOTE port must be between 1024 and 65535"`
 
-	UnsafeDisconnect   bool   `long:"unsafe-disconnect" description:"Allows the rpcserver to intentionally disconnect from peers with open channels. USED FOR TESTING ONLY."`
+	UnsafeDisconnect   bool   `long:"unsafe-disconnect" description:"DEPRECATED: Allows the rpcserver to intentionally disconnect from peers with open channels. THIS FLAG WILL BE REMOVED IN 0.10.0"`
 	UnsafeReplay       bool   `long:"unsafe-replay" description:"Causes a link to replay the adds on its commitment txn after starting up, this enables testing of the sphinx replay logic."`
 	MaxPendingChannels int    `long:"maxpendingchannels" description:"The maximum number of incoming pending channels permitted per peer."`
 	BackupFilePath     string `long:"backupfilepath" description:"The target location of the channel backup file"`
@@ -389,6 +389,7 @@ func loadConfig() (*config, error) {
 			Dir:     defaultLitecoindDir,
 			RPCHost: defaultRPCHost,
 		},
+		UnsafeDisconnect:   true,
 		MaxPendingChannels: DefaultMaxPendingChannels,
 		NoSeedBackup:       defaultNoSeedBackup,
 		MinBackoff:         defaultMinBackoff,