core90: work around dhcp client hang at shutdown after update.

config/rootfiles/core/90/update.sh

@@ -211,6 +211,10 @@ perl -e "require '/var/ipfire/lang.pl'; &Lang::BuildCacheLang"
 # Remove old udev configuration
 rm -vf /etc/udev/rules.d/30-persistent-network.rules
 
+# Remove pids from dhcp client because it hang at normal shutdown
+# so let the sysvinit kill it
+rm -f /run/dhcpcd-*.pid
+
 #
 # Start services
 #