Glanceclient implemented both functions before they landed into oslo.
Since both functions are already in oslo, it is now possible to pull
them in.
There's a small difference between glance's implementation and oslo's,
that is the later does not convert non-str objects - int, bool - to str
before trying to decode / encode them. This patch takes care of that
where necessary, more precisely, while encoding headers before doing a
new request.
Fixes bug: #1172253
Change-Id: I9a0dca31140bae28d8ec6aede515c5bb852b701b
7818387d4a