RFR [S]: 8227527: LogDecorations should lazily resolve host name

[Claes Redestad]

Hi,

reportedly the uname syscall taken to initialize logDecorations can
carry a small but measurable startup cost on some systems/platforms, so
the not-used-by-default _host_name should be lazily initialized.

Webrev:  http://cr.openjdk.java.net/~redestad/8227527/open.00/
Bug:     https://bugs.openjdk.java.net/browse/JDK-8227527
Testing: t1-3

Thanks!

/Claes