Fix HLTPrescaleCondAlg configuration
Some HLTPrescaleCondAlg configuration was missed out if flags was non-None. This caused a stall in TR:
ReadCondHandle 5 2 ERROR can't retrieve ( 'AthenaAttributeList' , 'ConditionStore+/TRIGGER/HLT/PrescaleKey' ) via base class [360026,289,t:1536143452,l:3,b:851]
HLTPrescaleCondAlg 4 1 FATAL Standard std::exception is caught [360026,1145,t:1536143452,l:3,b:3394]