Use system's coherence instead of elisa's

--- elisa-plugins-bad-0.5.9-1/elisa/plugins/discogs/discogs_resource.py	2008-09-08 18:11:49.000000000 +0200
+++ elisa-plugins-bad-0.5.9-1.new/elisa/plugins/discogs/discogs_resource.py	2008-09-15 16:22:35.000000000 +0200
@@ -35,7 +35,7 @@
 from twisted.internet import task
 
 from elisa.plugins.http_client.extern.client_http import ClientRequest
-from elisa.extern.coherence.et import parse_xml
+from coherence.extern.et import parse_xml
 
 import gzip, cStringIO