Memcached plugin: finally fix connection to unix socket files
Memcached plugin: finally fix connection to unix socket files

Sadly the last commit and PR 79 did not solve the issue completely.
Adding memcached servers connected via unix socket files through the
configuration string did not work as expected. So I decided to choose a
different approach by using libmemcached's memcached_server_add_*
functions to add servers and sockets. Beside socket connects now work
this has the other advantage to have return status codes for every
server that will be added.

cutelyst/cutelyst,cutelyst/cutelyst,buschmann23/cutelyst,buschmann23/cutelyst,buschmann23/cutelyst,cutelyst/cutelyst