Fix case error in qpid exchange name.  s/Direct/direct/

Fixes bug #1211338

(This is a minimal merge of just oslo-incubator bec54ac5 and
no other oslo changes.)

Change-Id: I129f9486f13be91868824e0e0534c4760d50589b
(cherry picked from commit 08e45107467fbf0ceb487ed0aebc55dc98a6da7d)
Merge "Fix case error in qpid exchange name.  s/Direct/direct/" into stable/grizzly
Merge branch 'stable/grizzly' of https://github.com/openstack/quantum into grizzly/stable