cubicweb #2602161 siteinfo: don't show the connectionless sessions, only count them [validation pending]

some load balancers ping regularly some instances, yielding A LOT OF small connection less sessions

we'd like to only count them, not show them all

prioritynormal
typebug
done in3.15.10
load0.200
load left0.000
closed by#b70295aaed9d [views/debug] Do not show all web sessions without CNX, just count them (closes #2602161)
patch[views/debug] Do not show all web sessions without CNX, just count them (closes #2602161) [applied]