Query strings are not _required_ to have slashes escaped, and in fact RFC
3986 suggests that "it is sometimes better for usability to avoid
percent-escaping those characters" (Section 3.4).
TripleO is currently unable to use the make_url function because its
database URLs contain slashes in the query, and end up in config files that
don't allow percent characters. This is probably not going to be an
isolated occurrence, so don't escape slashes in the query string.
Change-Id: I72f84e737b042ecfaabf5639c6164d46a072b423
adffed9273