Land #19932, Fix crash when running mssql payload against sessions

Author: cgranleese-r7

modules/exploits/windows/mssql/mssql_payload.rb

@@ -96,7 +96,7 @@ def execute_command(cmd, opts)
 
   def exploit
     if session
-      set_session(session.client)
+      set_mssql_session(session.client)
     else
       unless mssql_login_datastore
         print_status("Invalid SQL Server credentials")