CBLT-316:  only show tail of log files

Change-Id: I56e2e6debdce03666c4d9cf40a7c0986f37a9109
Reviewed-on: http://review.couchbase.org/38156
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>