Remove code dependent on the Sun NameService SPI (removed in Java 9)

[dvlato]

Test (and supporting classes) that used the NameService (DNI) SPI removed so our tests can be built on Java 9 and later, as the mentioned SPI has been removed from the JDK.

The test seemed to add little value as our GraphiteSender object can only be initialised now with a host and port instead of a resolved InetAddress object, so we consider that trying to migrate it to the "jdk.net.hosts.file" mechanism is not needed.

See:
https://www.oracle.com/technetwork/java/javase/9-removed-features-3745614.html
https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8134577

[mikkokar]

There is still some related configuration in proxy/pom.xml:

            -Dsun.net.spi.nameservice.provider.1=dns,local-dns
            -Dsun.net.spi.nameservice.provider.2=default
            -Dsun.net.inetaddr.ttl=0
            -Dsun.net.inetaddr.negative.ttl=0

I believe this can be removed.