Drop support for syslog logger

Change-Id: I11d3107cb0a1bdf01e87650a3b7894bae5029038
Reviewed-on: http://review.couchbase.org/25981
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>