#991 dtm: Support for broadcastless cluster formation

[Mathi Naickan]

Refer
https://sourceforge.net/p/opensaf/mailman/opensaf-users/thread/3BF98EC6E4C3B843B860540C1FA650421074CFDC%40planetdb4.netcracker.com/#msg32719137

[Anders Widell]

commit 1e62fa7bf9f3c5b4a6116cba6507cf679b268392 (HEAD -> develop, origin/develop)
Author: Anders Widell an..@..com
Date: Fri Oct 13 12:38:57 2017 +0200

dtm: Add support for using IP unicast to discover nodes [#991]

In addition to IP broadcast and IP multicast for DTM node discovery, add support
for IP unicast to a list of peer IP addresses. The list of IP addresses is read
when DTM starts, either from a file or using a DNS query.

commit 4ea8741b52153728e30e11c42aa120db12d7aae8
Author: Anders Widell an..@..com
Date: Thu Oct 12 22:13:32 2017 +0200

dtm: Extract Multicast class for node discovery message handling [#991]

Extract a class with the name Multicast, that handles send and receive of DTM
node discovery datagram messages. The underlying protocol can be IP broadcast,
IP multicast, and - implemented in this ticket: IP unicast.

Note that this refactoring isn't complete - the new class has private methods
that are in fact more or less unmodified copies of the old C functions.