Pass server configuration as an argument

The ServerCommonConf is now passed around as an argument instead of
being shared between components as a global variable. This allows for
more natural interaction with server.Session as a library and allows for
multiple servers to co-exist within the same process.

Related: #1387

g/g.go

@@ -6,16 +6,12 @@ import (
 
 var (
 	GlbClientCfg *ClientCfg
-	GlbServerCfg *ServerCfg
 )
 
 func init() {
 	GlbClientCfg = &ClientCfg{
 		ClientCommonConf: *config.GetDefaultClientConf(),
 	}
-	GlbServerCfg = &ServerCfg{
-		ServerCommonConf: *config.GetDefaultServerConf(),
-	}
 }
 
 type ClientCfg struct {
@@ -24,9 +20,3 @@ type ClientCfg struct {
 	CfgFile       string
 	ServerUdpPort int // this is configured by login response from frps
 }
-
-type ServerCfg struct {
-	config.ServerCommonConf
-
-	CfgFile string
-}