Remove a number of unneeded import os/bb calls

The bb and os modules are always imported so having these extra import calls
are a waste of space/execution time. They also set a bad example for people
copy and pasting code so clean them up.

(From OE-Core rev: 7d674820958be3a7051ea619effe1a6061d9cbe2)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/bugzilla.bbclass

@@ -72,7 +72,7 @@ def bugzilla_add_comment(debug_file, server, args, bug_number, text):
 
 addhandler bugzilla_eventhandler
 python bugzilla_eventhandler() {
-    import bb, os, glob
+    import glob
     import xmlrpclib, httplib
 
     class ProxiedTransport(xmlrpclib.Transport):