minimize use of "from module import *"

This statement was causing strange bugs because of namespace pollution. The
order of imports mattered because later "from module import *" statements would
overwrite modules imported earlier. Transitive imports also made it difficult
to figure out where an identifier was being imported.

This statement is still allowed in test code since nothing else should be
importing it.
diff --git a/src/python/oftest/dataplane.py b/src/python/oftest/dataplane.py
index 78089e3..f70de6c 100644
--- a/src/python/oftest/dataplane.py
+++ b/src/python/oftest/dataplane.py
@@ -18,13 +18,13 @@
 import os
 import socket
 import time
-import netutils
+import select
+import logging
 from threading import Thread
 from threading import Lock
 from threading import Condition
-import select
-import logging
-from ofutils import *
+import ofutils
+import netutils
 
 have_pypcap = False
 try:
@@ -161,7 +161,7 @@
         self.cvar = Condition()
 
         # Used to wake up the event loop from another thread
-        self.waker = EventDescriptor()
+        self.waker = ofutils.EventDescriptor()
         self.killed = False
 
         self.logger = logging.getLogger("dataplane")
@@ -320,7 +320,7 @@
             return None
 
         with self.cvar:
-            ret = timed_wait(self.cvar, grab, timeout=timeout)
+            ret = ofutils.timed_wait(self.cvar, grab, timeout=timeout)
 
         if ret != None:
             return ret