Move some code related to using JWT tokens from the `multi-tenancy.sh`
test case to `test/cases/api/common/common.sh`, `tools/provision.sh`
and `tools/run-mock-auth-servers.sh`. Move the composer and worker
configuration from the test to new testing configuration files.
The `tools/provision.sh` now accepts an optional argument specifying the
authentication method to use with the provisioned composer and workers.
Valid values are `tls` and `jwt`. If no argument is specified, the `tls`
option is used and the script defaults to its previous behavior.
