Fix output of info-tags-diff for new packages

Currently the output of info-tags-diff is different
when new packages are added and when tags are updated.
Example, if i add in a commit a new package:

- project: python-sphinx
  tags:
    test:

and update pike-uc tag for existing python-designateclient,
the output of info-tags-diff is:

python-designateclient ['pike-uc']
python-sphinx {'dependency': None}

This patch makes the same information and format for both cases:

python-designateclient ['pike-uc']
python-sphinx ['dependency']

Change-Id: I8a401490c8624db48b5137b8f21cac7f8a660fab

Author: amoralej

rdopkg/actionmods/rdoinfo.py

@@ -59,7 +59,7 @@ def tags_diff(info1, info2):
                 if pkg2['tags'][tag] != tag1:
                     updated_tags.append(tag)
         else:
-            updated_tags = pkg2.get('tags')
+            updated_tags = pkg2.get('tags').keys()
         if updated_tags:
             diff.append((pkg2['name'], updated_tags))
     return diff