Graphite: implement connection & socket timeout

[dolfinus]

Graphite class methods does not have any explicit timeout. So when Graphite instance is not available, experiencing network issues or is overloaded with too many requests, reporter may hang for some long time.

In my case (Spark metrics sink sending reports to Graphite) the lack of timeouts prevents Spark session from being stopped if Graphite instance is overloaded. This can last 5-10 minutes, sometimes even more.

What's changed:

• Add connectionTimeoutMs argument to Graphite constructor (default 500ms)
• Add socketTimeoutMs argument to Graphite constructor (default 5s)

[dolfinus]

Closed because socket.setSoTimeout(...) can be used only to set timeout of read operations, but not write operations which are used by this sender. Java sockets don't support timeout for write operations at all. The only way to implement this is using some kind of non-blocking IO.