daemon: Allow overriding NOFILES ulimit for the daemon as well

One of my latest patches (d8db0f96) created support for setting
the limit for the maximum of opened files by qemu user. However,
since libvirtd keeps one FD opened per domain (well, for qemu at least)
it will likely hit this limit on huge scenarios.

daemon/libvirtd.init.in

@@ -60,6 +60,13 @@ start() {
     echo -n $"Starting $SERVICE daemon: "
     mkdir -p @localstatedir@/cache/libvirt
     rm -rf @localstatedir@/cache/libvirt/*
+
+    # LIBVIRTD_NOFILES_LIMIT from /etc/sysconfig/libvirtd is not handled
+    # automatically
+    if [ -n "$LIBVIRTD_NOFILES_LIMIT" ]; then
+        ulimit -n "$LIBVIRTD_NOFILES_LIMIT"
+    fi
+
     KRB5_KTNAME=$KRB5_KTNAME daemon --pidfile $PIDFILE --check $SERVICE $PROCESS --daemon $LIBVIRTD_CONFIG_ARGS $LIBVIRTD_ARGS
     RETVAL=$?
     echo

daemon/libvirtd.service.in

@@ -15,6 +15,8 @@ Before=libvirt-guests.service
 EnvironmentFile=-/etc/sysconfig/libvirtd
 ExecStart=@sbindir@/libvirtd $LIBVIRTD_ARGS
 ExecReload=/bin/kill -HUP $MAINPID
+# Override the maximum number of opened files
+#LimitNOFILE=2048
 
 [Install]
 WantedBy=multi-user.target

daemon/libvirtd.sysconf

@@ -19,3 +19,6 @@
 #QEMU_AUDIO_DRV=sdl
 #
 #SDL_AUDIODRIVER=pulse
+
+# Override the maximum number of opened files
+#LIBVIRTD_NOFILES_LIMIT=2048

daemon/libvirtd.upstart

@@ -31,6 +31,11 @@ script
         ulimit -c "$DAEMON_COREFILE_LIMIT"
     fi
 
+    # LIBVIRTD_NOFILES_LIMIT from /etc/sysconfig/libvirtd is not handled
+    # automatically
+    if [ -n "$LIBVIRTD_NOFILES_LIMIT" ]; then
+        ulimit -n "$LIBVIRTD_NOFILES_LIMIT"
+    fi
     mkdir -p /var/cache/libvirt
     rm -rf /var/cache/libvirt/*