BUG/MEDIUM: init: Initialize idle_orphan_conns for first server in server-template

BUG/MEDIUM: init: Initialize idle_orphan_conns for first server in server-template

When initializing server-template all of the servers after the first
have srv->idle_orphan_conns initialized within server_template_init()
The first server does not have this initialized and when http-reuse
is active this causes a segmentation fault when accessed from
srv_add_to_idle_list().  This patch removes the check for
srv->tmpl_info.prefix within server_finalize_init() and allows
the first server within a server-template to have srv->idle_orphan_conns
properly initialized.

This should be backported to 1.9.