Fix case error in qpid exchange type "direct"

Original-bug: #1211338

Most places correctly have "direct", but one place has "Direct"
instead, which is incorrect.

(cherry picked from commit bec54ac5fb6a190c98079537f63d2f0e17584d21)

Change-Id: I4681f04534bc27b2571774766d34121b37ebcf45
Merge "Fix case error in qpid exchange type "direct"" into stable/grizzly