header: install test mock headers

IPMI Blob handlers will need to include these mocks when building
unit-tests.  Therefore, they must be installed.

Change-Id: I4c8ed0fa1a4a8912853c024206ef5e61f87707d8
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/manager_unittest.cpp b/test/manager_unittest.cpp
index c0157e6..a4c7a8c 100644
--- a/test/manager_unittest.cpp
+++ b/test/manager_unittest.cpp
@@ -1,7 +1,6 @@
-#include "blob_mock.hpp"
-
 #include <algorithm>
 #include <blobs-ipmid/manager.hpp>
+#include <blobs-ipmid/test/blob_mock.hpp>
 #include <string>
 #include <vector>