Fix internal server error due to unpacking TestJobUser.
Fix internal server error due to unpacking TestJobUser.

This is a follow up to commit 5415eafa78a30b2f5f74e93fcfb3c08e2bc4422a which
fixes creating TestJobUser.

Change-Id: If8a6c5697cca596503a22c075f973b3f5b09de4e

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server