Update port information

Dockerfile

   rm unifi_sysvinit_all.deb && \
   ln -s /var/lib/unifi /usr/lib/unifi/data
 
-RUN ln -s /var/lib/unifi /usr/lib/unifi/data
-
-EXPOSE 8080 8081 8443 8843 8880
+EXPOSE 8080 8443 8843 8880
 
 VOLUME ["/var/lib/unifi"]
 

README.md

               csmith/unifi:4.8.18
 ```
 
-Port 8443 is used for the HTTPS web interface, port 8080 used by APs.
+The container exposes these ports:
+
+  * 8080 (used by the UAPs to send messages to the controller)
+  * 8443 (admin web interface, HTTPS)
+  * 8843 (HTTPS captive portal redirection)
+  * 8880 (HTTP captive portal redirection)
 
-The Dockerfile exposes these ports: 8081 8443 8843 8880