The memcache_servers configuration option is declared as a ListOpt,
but when used in AuthProtocol.__init__(), we treat it as a string
to be split on ',', which is wrong. Remove the .split().
No test is added because the memcache package may not be installed,
and I cannot see an easy method to only test this clause if it is
available.
Fixes bug 1086125.
Change-Id: Ifb0a18017d2407b3ccb2188b1a704c26997ba594