PluginCache: Check plugin name before trying to iteritems
PluginCache: Check plugin name before trying to iteritems

Currently if your config contains

typo_for_a_global_alias: 1

You will get an error where we try to call 'iteritems' on the value 1. This
commit re-orders the checks so that you instead get an error for the
unrecognised 'typo_for_a_global_alias'.

lisatn/workload-automation,setrofim/workload-automation,lisatn/workload-automation,setrofim/workload-automation,setrofim/workload-automation,lisatn/workload-automation,ARM-software/workload-automation,ARM-software/workload-automation,ARM-software/workload-automation,setrofim/workload-automation,ARM-software/workload-automation,lisatn/workload-automation