Tools: Allow access for administrators from bastions

At the moment, to access execution nodes administrators need to log
into tools-login or tools-dev and then use HBA to access the hosts.
This makes it very cumbersome to use utilities like pdsh to execute
commands on all Tools instances.

This change allows standard, non-HBA ssh-via-bastion access for
members of the tools.admin group.

Change-Id: I6ac7cae1101c7687fa03a9c982e6e8f7f0de2d7a