sys_util: don't use hostname in syslog message header
sys_util: don't use hostname in syslog message header

The putting the hostname in the syslog header of messages sent to
/dev/log isn't widely supported. It isn't understood by rsyslogd by
default, and it isn't understood by journald. Remove it as it provides
no value to us.

BUG=None
TEST=Ensure journal properly parses the header from crosvm log messages

Change-Id: I9bba78925f048f7d2ce6320b00b9fa52f070ce51
Reviewed-on: https://chromium-review.googlesource.com/1525139
Commit-Ready: Christopher Morin <179a691731164b620c69e181d7c3d55ceebe202f@google.com>
Tested-by: Christopher Morin <179a691731164b620c69e181d7c3d55ceebe202f@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm