'paramiko.transport DEBUG: EOF in transport thread' Error during ssh connection

paramiko.transport DEBUG: EOF in transport thread error could be seen in some raring (mostly server) smoke tests intermittently. The following is seen in some of raring smoke tests mostly during when there are a number of VMs running on the host.

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/utah/run.py", line 240, in run_tests
    machine.installclient()
  File "/usr/lib/python2.7/dist-packages/utah/provisioning/provisioning.py", line 402, in installclient
    returncode, _stdout, stderr = self.run(install_command, root=True)
  File "/usr/lib/python2.7/dist-packages/utah/provisioning/ssh.py", line 100, in run
    key_filename=config.sshprivatekey)
  File "/usr/lib/python2.7/dist-packages/paramiko/client.py", line 301, in connect
    t.start_client()
  File "/usr/lib/python2.7/dist-packages/paramiko/transport.py", line 461, in start_client
    raise e
EOFError

utah-server-ssh.log contains the following
2013-03-21 07:52:32,319 ssh DEBUG: Connecting SSH
2013-03-21 07:55:52,385 paramiko.transport DEBUG: starting thread (client mode): 0x2bb0d90L
2013-03-21 07:55:52,395 paramiko.transport INFO: Connected (version 2.0, client OpenSSH_6.1p1)
2013-03-21 07:55:52,396 paramiko.transport DEBUG: EOF in transport thread
2013-03-21 07:55:52,409 ssh INFO: Removing machine addresses from ssh known_hosts file

I could not do more investigation on this since the VM's have been destroyed.

Some of the impacted jobs are,
https://jenkins.qa.ubuntu.com/view/Raring/view/Smoke%20Testing/job/raring-server-i386-smoke-dns-server/130/
https://jenkins.qa.ubuntu.com/view/Raring/view/Smoke%20Testing/job/raring-server-i386-smoke-mail-server/132/