MINOR: server: Copy configuration file and line for server templates

When servers based on server templates are initialized, the configuration file
and line are now copied. This helps to emit understandable warning and alert
messages.

This patch may be backported if needed, as far as 1.8.
diff --git a/src/server.c b/src/server.c
index 4b7d7d7..42c2e54 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1862,6 +1862,9 @@
 		if (!newsrv)
 			goto err;
 
+		newsrv->conf.file = strdup(srv->conf.file);
+		newsrv->conf.line = srv->conf.line;
+
 		srv_settings_cpy(newsrv, srv, 1);
 		srv_prepare_for_resolution(newsrv, srv->hostname);
 #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME