chronyc: Update help text parsing

In chrony-2.2 the chronyc help text formating was changed, the command
descriptions now may be on muliple lines and the commands are divided in
sections.

completions/chronyc

@@ -28,7 +28,7 @@ _chronyc()
     case $args in
         0)
             COMPREPLY=( $( compgen -W "$( $1 help 2>/dev/null | \
-                awk 'NR > 1 { sub("\\|", " ", $1); print $1 }' )" -- "$cur" ) )
+                awk '!/(^ |: *$)/ { sub("\\|", " ", $1); print $1 }' )" -- "$cur" ) )
             ;;
         1)
             case $prev in