Fix template_dirs handling for django1.7
Fix template_dirs handling for django1.7

Need a tuple to concatenate with a tuple.

Change-Id: I8b0b9d012f1f5b2304575d3f186e227ad8ef971d

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