BUG/MINOR: peers: Incomplete peers sections should be validated.

Before supporting "server" line in "peers" section, such sections without
any local peer were removed from the configuration to get it validated.

This patch fixes the issue where a "server" line without address and port which
is a remote peer without address and port makes the configuration parsing fail.
When encoutering such cases we now ignore such lines remove them from the
configuration.

Thank you to Jérôme Magnin for having reported this bug.

Must be backported to 2.1 and 2.0.
diff --git a/include/proto/server.h b/include/proto/server.h
index 2847a8c..f8fed31 100644
--- a/include/proto/server.h
+++ b/include/proto/server.h
@@ -46,7 +46,7 @@
 int srv_downtime(const struct server *s);
 int srv_lastsession(const struct server *s);
 int srv_getinter(const struct check *check);
-int parse_server(const char *file, int linenum, char **args, struct proxy *curproxy, struct proxy *defproxy, int parse_addr);
+int parse_server(const char *file, int linenum, char **args, struct proxy *curproxy, struct proxy *defproxy, int parse_addr, int in_peers_section);
 int update_server_addr(struct server *s, void *ip, int ip_sin_family, const char *updater);
 const char *update_server_addr_port(struct server *s, const char *addr, const char *port, char *updater);
 struct server *server_find_by_id(struct proxy *bk, int id);