[datafeed parser] fix retrieve_url to always return urllib2.urlopen compatible output
as one should expect to be able to call geturl/getcode/info on the returned
object whatever the url he gave.
Related to #3682069
addressbook
basket
blog
book
calendar
comment
company
email
file
folder
i18ncontent
keyword
link
mailinglist
person
tag
timeseries
vcsfile