Description of problem:
While registering the host using the Global Registration template

Configuring REX Pull Mode while registering the host using Global registration template should notify if MQTT is not enabled in the Capsule host. Since the registration curl command throws below error during registration which is expected.

~~~
● The yggdrasil daemon is inactive

Manage your Red Hat connector systems: https://red.ht/connector

yggdrasild failed to start! Check configuration in /etc/yggdrasil/config.toml and make sure the broker is running on the server.
~~~

On the other hand, if the MQTT is enabled in the capsule server, the "yggdrasild" service starts without any error.

Version-Release number of selected component (if applicable):
6.15

How reproducible:
100%

Steps to Reproduce:
1. Ensure, No pull-based transport -MQTT is enabled in capsule host
1. Register a host using the global registration template and select "REX pull mode - Yes (override).

Actual results:
The "yggdrasild" service failed when configuring REX pull mode using a global registration template.

Expected results:
Pop-up notification while selecting "REX pull mode" when MQTT is not configured in the capsule.
This may avoid "yggdrasild" service failure in the client host during registration and unnecessary troubleshooting.