Make test_snapshot_pattern ssh error path work

When validation was added to all ssh connections this means that the
exception handling code around ssh connections was actually run, a bug
was fixed in the exception logging for test_snapshot_pattern. It also
reraises the error so we know that the failure was caused by the ssh
connection

Change-Id: Iadccef5046e8884fce54ba2cea591a6e86a8b318
diff --git a/tempest/scenario/test_snapshot_pattern.py b/tempest/scenario/test_snapshot_pattern.py
index ab335e2..d41490a 100644
--- a/tempest/scenario/test_snapshot_pattern.py
+++ b/tempest/scenario/test_snapshot_pattern.py
@@ -49,8 +49,9 @@
         try:
             return self.get_remote_client(server_or_ip)
         except Exception:
-            LOG.exception()
+            LOG.exception('Initializing SSH connection failed')
             self._log_console_output()
+            raise
 
     def _write_timestamp(self, server_or_ip):
         ssh_client = self._ssh_to_server(server_or_ip)