remove need for iterable depset in onos catalog generator

Change-Id: Id1cc9022c94a212421a71cb2f738187ffcee05e5
(cherry picked from commit 6fb814f45357398411d9343b615eac3b8ec6c0e8)
diff --git a/tools/build/bazel/publish_catalog.bzl b/tools/build/bazel/publish_catalog.bzl
index edf9569..199d67e 100644
--- a/tools/build/bazel/publish_catalog.bzl
+++ b/tools/build/bazel/publish_catalog.bzl
@@ -33,7 +33,7 @@
             packaging = classifier
             classifier = None
 
-    for f in target.files:
+    for f in target.files.to_list():
         print("%s\t%s" % (f.path, _remote(group_id, artifact_id, version, packaging, classifier)))
     return []