Keep attempting to bring up the network

After a total power outage (system and networking gear), it's possible
that the system boots up and blow through all the timeouts for DHCP
before the network is operational. Unfortunately, I can't always solve
that.

scripts/init-bottom/tailscale

@@ -33,6 +33,7 @@ wait_for_tailscaled()
     # SC3043: In POSIX sh, 'local' is undefined.
     local pid exe timer="$TAILSCALE_SHUTDOWN_TIMEOUT"
     pid="$(cat "$PIDFILE" 2>/dev/null)" || return 1
+    rm -f "$PIDFILE"
 
     while [ $timer -gt 0 ] && exe="$(readlink -f "/proc/$pid/exe" 2>/dev/null)"; do
         if [ "$exe" = "$EXE" ]; then
@@ -60,8 +61,6 @@ if PID="$(wait_for_tailscaled)"; then
     log_end_msg
 fi
 
-rm -f "$PIDFILE"
-
 if [ "$BOOT" != nfs ] && [ "$IFDOWN" != none ]; then
     for IFACE in /sys/class/net/$IFDOWN; do
         [ -e "$IFACE" ] || continue