Limit number of atoms used by ejabberdctl ( #2977)

Cherry-picked from ejabberd upstream 20.03-21-g762486d19
and 20.03-22-geac7e3488

ecs/bin/ejabberdctl

@@ -218,7 +218,7 @@ uid()
     uuid=$(uuidgen 2>/dev/null)
     [ -z "$uuid" ] && [ -f /proc/sys/kernel/random/uuid ] && uuid=$(cat /proc/sys/kernel/random/uuid)
     [ -z "$uuid" ] && uuid=$(printf "%X" "${RANDOM:-$$}$(date +%M%S)")
-    uuid=${uuid%%-*}
+    uuid=$(printf '%s' $uuid | sed 's/^\(...\).*$/\1/')
     [ $# -eq 0 ] && echo "${uuid}-${ERLANG_NODE}"
     [ $# -eq 1 ] && echo "${uuid}-${1}-${ERLANG_NODE}"
     [ $# -eq 2 ] && echo "${uuid}-${1}@${2}"