Fix typo in method call

s/displayName/printableName/g
Fix warnings when the port is disabled
Fix uninstallation of webserver

HAproxy was unable to restart until HAProxyServices is regenerated from a RW instance.
Fix when webserver is not listening in HTTP port
Check, at least, a listening port is mandatory
Merge pull request #1124 from Zentyal/ejhernandez/haproxy-webserver-fixes

Several fixes on HAProxy and WebServer (all related)