[Bug]: Azure gateways do not work

[jvstme]

Steps to reproduce

1. Create an Azure gateway.

   > cat gateways/azure.dstack.yml 
   type: gateway
   name: azure
   backend: azure
   region: westeurope
   domain: azure.example.com
   
   > dstack apply -y gateways/azure.dstack.yml
   

2. Set DNS A records for the gateway's wildcard domain.
3. Try running a service with the gateway.

   > cat services/.dstack.yml 
   type: service
   gateway: azure
   image: nginx
   port: 80
   https: false
   
   > dstack apply -f services/.dstack.yml
   

Actual behaviour

https: false services are registered successfully but are not responsive.

> curl --verbose --max-time 10 http://dangerous-falcon-1.azure.example.com
* Host dangerous-falcon-1.azure.example.com:80 was resolved.
* IPv6: (none)
* IPv4: 51.145.137.34
*   Trying 51.145.137.34:80...
* Connection timed out after 10002 milliseconds
* closing connection #0
curl: (28) Connection timed out after 10002 milliseconds

https: true services are not registered, even though DNS records are set correctly.

Submit a new run? [y/n]: y
Error obtaining tricky-insect-1.azure.example.com TLS certificate:
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Some challenges have failed.

Expected behaviour

Both https: false and https: true services are registered successfully and responsive.

dstack version

0.18.33

Server logs

No response

Additional information

Both symptoms may mean that connections to port 80 are blocked by a firewall. Whether port 443 is blocked is to be determined.