The connect_socket() can be called with @server argument being
set to a hostname that's different to "localhost" but in fact is
localhost. In this case, and when @allow_server_override is set,
the function connects to "localhost". Well, the leak exists
because in aforementioned case the @server variable is
overwritten. And since it is plain 'char *' it has to be
strdup()-ed. But switching it to 'const char *', it can be set to
"localhost" literal. Similarly, @port

 is constant and unchanged
withing the function and thus should be type of 'const char *'.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>