Removed assignment of global_parameters.server->host by gethostname() in

Removed assignment of global_parameters.server->host by gethostname() in
src/config.c, if listen/@host is empty.
   This had the very unpleasent side effect in src/http.c:980 in function
void http_init(const char *addr) that the if statement 'if (pp)' got triggered,
with the string 'flurry:9090' (in mine config) and therefore the only bind has
beem made to the loop-back device. As a consequence, pazpar2/masterkey could
only be accessed from localhost, which is kind of very useless.
   What is really needed is that the global_parameters.server->host variable
is set to gethostname() in such a way that we are sure to go into the 'else'
of the above 'if (pp)', such that we still are listening to all existing
interfaces.
   I tried to do this by assigning
global_parameters.server->host = gethostname() using a nmem_strdup(9, but
failed due to the fact that I have no access to the correct nmem memory
handler here. See src/http.c:1009 for details.
   Still, I would like to have set
global_parameters.server->host = gethostname() somewhere to ensure the
'Via:' header is correct.