Fix swiftclient.client.quote() for Python 3

On Python 3, urllib.parse.quote() accepts bytes and str (unicode) types and
always return str (unicode).

Add also more tests with non-ASCII characters.

Change-Id: I8e0f19da7240e874392327d0da074ed4abb7d213
Merge "Fix swiftclient.client.quote() for Python 3"