Include ip address for ssh_connect exception

Add some sort of server information about our failed ssh_connect
attempts.  Currently we don't expose any information about the host.

2016-08-23 16:26:11,894 ERROR nodepool.utils: Exception while testing ssh access:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/nodepool/nodeutils.py", line 55, in ssh_connect
    client = SSHClient(ip, username, **connect_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/nodepool/sshclient.py", line 30, in __init__
    key_filename=key_filename)
  File "/usr/local/lib/python2.7/dist-packages/paramiko/client.py", line 305, in connect
    retry_on_signal(lambda: sock.connect(addr))
  File "/usr/local/lib/python2.7/dist-packages/paramiko/util.py", line 270, in retry_on_signal
    return function()
  File "/usr/local/lib/python2.7/dist-packages/paramiko/client.py", line 305, in <lambda>
    retry_on_signal(lambda: sock.connect(addr))
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
error: [Errno 110] Connection timed out

Change-Id: I5705798c91b228a7be2788c33c5a128653b24bbe
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

nodepool/nodeutils.py

@@ -61,7 +61,8 @@ def ssh_connect(ip, username, connect_kwargs={}, timeout=60):
                      (username, ip, count))
         except socket.error as e:
             if e[0] not in [errno.ECONNREFUSED, errno.EHOSTUNREACH, None]:
-                log.exception('Exception while testing ssh access:')
+                log.exception(
+                    'Exception while testing ssh access to %s:' % ip)
 
     out = client.ssh("test ssh access", "echo access okay", output=True)
     if "access okay" in out: