cmd/bosun: fix seriesFunc tags function
cmd/bosun: fix seriesFunc tags function

bookingcom/bosun,simnv/bosun,simnv/bosun,simnv/bosun,csmith-palantir/bosun,bosun-monitor/bosun,simnv/bosun,csmith-palantir/bosun,bookingcom/bosun,mhenderson-so/bosun,csmith-palantir/bosun,mhenderson-so/bosun,mhenderson-so/bosun,bookingcom/bosun,bosun-monitor/bosun,simnv/bosun,bookingcom/bosun,bosun-monitor/bosun,bosun-monitor/bosun,csmith-palantir/bosun,mhenderson-so/bosun,bookingcom/bosun,mhenderson-so/bosun,mhenderson-so/bosun,bosun-monitor/bosun,simnv/bosun,csmith-palantir/bosun,csmith-palantir/bosun,bosun-monitor/bosun,bookingcom/bosun