ssh: Disable forwardings

When port forwardings are configured in the ssh config and a parallel
ssh session with the same sever is already open, ssh will print error
messages. Do the same as scp to prevent them and pass the
ClearAllForwardings option to the ssh client.
Do the same for X11 forwardings.

bmaptools/TransRead.py

@@ -502,6 +502,8 @@ def _open_url_ssh(self, parsed_url):
                 "-p" + password,
                 "ssh",
                 "-o StrictHostKeyChecking=no",
+                "-o ClearAllForwardings=yes",
+                "-o ForwardX11=no",
                 "-o PubkeyAuthentication=no",
                 "-o PasswordAuthentication=yes",
                 hostname,
@@ -517,6 +519,8 @@ def _open_url_ssh(self, parsed_url):
             popen_args = [
                 "ssh",
                 "-o StrictHostKeyChecking=no",
+                "-o ClearAllForwardings=yes",
+                "-o ForwardX11=no",
                 "-o PubkeyAuthentication=yes",
                 "-o PasswordAuthentication=no",
                 "-o BatchMode=yes",