Avoid timeseries read operations to display the chart icon

Now the icon is displayed whenever the timeseries are enabled for the given context

scripts/lua/modules/as_utils.lua

@@ -1,6 +1,5 @@
 require "lua_utils"
 require "graph_utils"
-local ts_utils = require "ts_utils"
 
 -- Get from redis the throughput type bps or pps
 local throughput_type = getThroughputType()
@@ -33,7 +32,7 @@ function as2record(ifId, as)
 
    record["column_chart"] = ""
 
-   if ts_utils.exists("asn:traffic", {ifid=ifId, asn=as["asn"]}) then
+   if areASTimeseriesEnabled(ifId) then
       record["column_chart"] = '<A HREF="'..ntop.getHttpPrefix()..'/lua/as_details.lua?asn='..as["asn"]..'&page=historical"><i class=\'fas fa-chart-area fa-lg\'></i></A>'
    end