Revert "Revert "Update the syslog_aggregator job to use vendor nats""

This reverts commit c6fae32f631fee8e453739099f43f9d7bd6a293d.
Bump yetis: apps cant reach loggregator machines

Signed-off-by: Stephan Hagemann <stephan@pivotallabs.com>
Revert "Revert "Revert "Update the syslog_aggregator job to use vendor nats"""

This reverts commit 8053bc96079db04c48c4eca92c1a14803802f660.