Add std out to ssh exception.

Some commands in case of error redirect his output in stdout
instead of stderr. I suggest to combine stdout and stderr and pass
this string to ssh exception. It will help to understand better
errors in ssh tests.

Change-Id: Ied28043f0eaefa1c3a00b7e98e52b13a86873827

tempest_lib/common/ssh.py

@@ -143,7 +143,7 @@ class Client(object):
         if 0 != exit_status:
             raise exceptions.SSHExecCommandFailed(
                 command=cmd, exit_status=exit_status,
-                strerror=''.join(err_data))
+                stderr=err_data, stdout=out_data)
         return ''.join(out_data)
 
     def test_connection_auth(self):

tempest_lib/exceptions.py

@@ -184,4 +184,5 @@ class SSHTimeout(TempestException):
 class SSHExecCommandFailed(TempestException):
     """Raised when remotely executed command returns nonzero status."""
     message = ("Command '%(command)s', exit status: %(exit_status)d, "
-               "Error:\n%(strerror)s")
+               "stderr:\n%(stderr)s\n"
+               "stdout:\n%(stdout)s")