Cleanup transport along RPC clients
Cleanup transport along RPC clients

This fixes a bad weird condition in the API server related to
cron-triggers and SIGHUP. The parent API server creates a RPC connection
when creating workflows from cron. If a SIGUP signal happens after, the
child inherits the connection, but it's non-functional.

Change-Id: Ic98e2db02abd8483591756d73e06784cc2e9cbe3
Closes-Bug: #1789680

openstack/mistral,openstack/mistral