nginx: Add missing logrotate script

roles/nginx/files/nginx-logrotate.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+set -eu
+
+cd /var/www/logs
+
+find_rotated() {
+    find . -mindepth 1 -maxdepth 1 -type f -name "${1}.*" | sort -V -r
+}
+
+for log in *.log ; do
+    find_rotated "$log" | while read -r name; do
+        ext="${name##*.}"
+        next="${name%.*}.$((ext+1))"
+	mv "$name" "$next"
+    done
+    mv "$log" "${log}.1"
+    touch "$log"
+
+    find_rotated "$log" | while read -r name; do
+        num="$(echo "$name" | awk -F. '{ print $NF }')"
+	if [ "$num" -gt 7 ]; then
+            rm -f "$log"
+	fi
+    done
+done
+
+kill -USR1 "$(cat /var/run/nginx.pid)"