15828: Configured workbench is a "trusted client" by default

Sidestep an installation sinkhole that almost everyone seems to fall into.

This makes it so it is no longer necessary to explicitly set
"is_trusted" on an api_client record for the system configured
Workbench instances to solve the "client cannot manipulate other's
tokens" permission error.

Arvados-DCO-1.1-Signed-off-by: Peter Amstutz <pamstutz@veritasgenetics.com>