I have found a new workaround in order to walk through the annoying message:
Basically, you have to hack your own configuration if you don’t want to change your settings on the terminal server.
If using RDP 6 client or above:
mstsc /v IPADDRESS /admin
If using older than RDP 6:
mstsc /v IPADDRESS /console
With this command you can open one extra session. But if administrator is logged you cannot kick him our. This is valid only for regular users.
net use \\server
net use /user:[username] \\server\share
Now we are executing commands for the server name/IP we have just enter info about.
query session /server:servername
With this command you will review all active sessions. You have to choose which user/administrator to kick out of the server in order to take his place inside. Once you did this, enter the following command:
reset session [ID] /server:servername
Other possible commands for session reset:
rwinsta session [ID] /server:servername