Fix the logic in e1f44097
Fix the logic in e1f44097

load_devicetype_template returns str or None, so turn
it into a bool for the validity check.

Change-Id: I5fcea43c277af97a989be5c07570c088c882b2e8

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