BUG/MEDIUM: dns/server: fix incomatibility between SRV resolution and server state...

BUG/MEDIUM: dns/server: fix incomatibility between SRV resolution and server state file

Server state file has no indication that a server is currently managed
by a DNS SRV resolution.
And thus, both feature (DNS SRV resolution and server state), when used
together, does not provide the expected behavior: a smooth experience...

This patch introduce the "SRV record name" in the server state file and
loads and applies it if found and wherever required.

This patch applies to haproxy-dev branch only. For backport, a specific patch
is provided for 1.8.