Fix lazy translation UnicodeErrors

upload_utils is concatenating str and Message objects which doesn't work
on python 2, so change the str to a unicode object.

test_quota.py was casting Message objects to str which fails for the
same reason, so rather than cast to str, cast using six.text_type.

See oslo commit 2cfc1a78d8063cf20083cf7df796d730a576551c for history and
details on why the Message object doesn't support __str__ casting.

This is a small part of a larger effort that the oslo team will be
rolling out with graduation and adoption of the oslo-i18n library.

Closes-Bug: #1334774

Conflicts:
	glance/api/v1/upload_utils.py
	glance/tests/unit/test_quota.py

Change-Id: I9d3f29c661f1afffabbbbb499f48d37ef5a8fcee
(cherry picked from commit 834e1f2150c6f2afd92036e6b7f53afee4006682)