Fix console buffer interaction

In some environments, the read method on the pipe object fails
to work, os.read should be the same, but seems to work better and
is happy to perform the opportunisticly large reads I want.

confluent_server/confluent/consoleserver.py

@@ -74,7 +74,7 @@ def get_buffer_output(nodename):
         select.select((instream,), (), (), 30)
         while not outdata or outdata[-1]:
             try:
-                chunk = instream.read(128)
+                chunk = os.read(instream.fileno(), 128)
             except IOError:
                 chunk = None
             if chunk: