Add support for custom shm_size for seed container(s)

It's now possible to change Docker's default 64M SHM size
for custom containers running on the seed.

Change-Id: Ic6c2ec38e8a22b8acc90e17a552e471aa8313f7d

ansible/roles/deploy-containers/tasks/deploy.yml

@@ -25,6 +25,7 @@
     ports: "{{ container_config.ports | default(omit) }}"
     privileged: "{{ container_config.privileged | default(omit) }}"
     restart_policy: "{{ container_config.restart_policy | default(deploy_containers_defaults.restart_policy) }}"
+    shm_size: "{{ container_config.shm_size | default(omit) }}"
     sysctls: "{{ container_config.sysctls | default(omit) }}"
     timeout: "{{ deploy_containers_docker_api_timeout }}"
     ulimits: "{{ container_config.ulimits | default(omit) }}"

doc/source/configuration/reference/seed-custom-containers.rst

@@ -44,6 +44,7 @@ Possible options for container deployment:
        ports:
        privileged:
        restart_policy:
+       shm_size:
        sysctls:
        tag:
        ulimits:

releasenotes/notes/add-seed-container-shm-size-support-ffc5976fb87fe285.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Adds support for changing ``shm_size`` parameter when deploying
+    custom seed container(s).