Fix typo in tag handling
Fix typo in tag handling

Closes: #1316249 - discrepancy between
the unit test and the runtime code caused
by a typo in the field to retrieve from
the submitted JSON.

Change-Id: Idc2eb00d97854363cf82552b318b0c885a6a8bde
Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server