Add type for mtu field in docker role

Closes-Bug: #2066032

This patch adds an integer type to the task in the docker role that
generates the docker daemon config. This was previously uncast and
defaulting to a string type, which causes an error with certain docker
versions (via the Rocky 9.3 distro). See bug description for more info.

Change-Id: I2a996fa22fedece2c894b378fadbfc5dd0c045b6

ansible/roles/docker/tasks/main.yml

@@ -11,7 +11,7 @@
       {%- set _ = options.update({"registry-mirrors": docker_registry_mirrors}) -%}
       {%- endif -%}
       {%- if docker_daemon_mtu -%}
-      {%- set _ = options.update({"mtu": docker_daemon_mtu}) -%}
+      {%- set _ = options.update({"mtu": docker_daemon_mtu | int}) -%}
       {%- endif -%}
       {%- if docker_daemon_live_restore | bool -%}
       {%- set _ = options.update({"live-restore": docker_daemon_live_restore | bool}) -%}