fix: [postgres] prevent failure on slower hosts

Using ``docker stop CONTAINER`` followed by a ``docker rmi IMAGE``
where IMAGE is the image of CONTAINER may fail. To ensure that it won't
fail, we have to wait for the disappearance of the container in the
container list.

postgres/actions/upgrade

@@ -101,6 +101,36 @@ postgres:container:version() {
     echo "$image_version"
 }
 
+## XXXvlab: there's an issue with using ``docker stop ..``, then
+## ``docker rmi ..`` on the stopped container's image. It can fail on
+## some VPS (and on dev platform) saying the image is still in use.
+docker:container:stop() {
+    local container=$1 timeout=${2:-60}
+
+    ## Stop the container
+    if ! out=$(docker stop "$container"); then
+        err "Failed to stop container $container"
+        echo "$out" | prefix "  | " >&2
+        return 1
+    fi
+
+    local start=$SECONDS
+
+    # Wait for the container to stop
+    while [ -n "$(
+        curl -s --unix-socket /var/run/docker.sock \
+		http://localhost/containers/json?all=1 |
+		jq -r '.[] | .Id[:12] , .Id , ( .Names | .[] | ltrimstr("/"))' | grep ^"$container"$)" ]; do
+        if [ $(($SECONDS - start)) -ge $timeout ]; then
+            err "Timeout waiting for container '$container' to stop." >&2
+            return 1
+        fi
+        sleep 0.1
+    done
+    return 0
+}
+
+
 postgres:container:psql () {
     local container="$1"
     docker exec -i "$container" psql 2>&1
@@ -290,9 +320,8 @@ while [[ "${#upgrade_path[@]}" != 0 ]]; do
                         break
                     fi
 
-                    out=$(docker stop "$migration_container" 2>&1) || {
-                        err "Failed to stop the dump container $migration_container for $current_image_version:"
-                        printf "%s\n" "$out" | prefix "  ${GRAY}|${NORMAL} "
+                    docker:container:stop "$migration_container" || {
+                        err "Failed to stop the dump container $migration_container for $current_image_version"
                         break 3
                     }
                     expected_stop="1"
@@ -328,6 +357,8 @@ while [[ "${#upgrade_path[@]}" != 0 ]]; do
             out=$(docker rmi "$current_image" 2>&1) || {
                 err "Failed to remove image $current_image"
                 printf "%s\n" "$out" | prefix "  ${GRAY}|${NORMAL} "
+		        sleep 2
+	            docker start "$migration_container" >&2
                 break 2
             }
         }
@@ -390,9 +421,8 @@ while [[ "${#upgrade_path[@]}" != 0 ]]; do
 
                     current_image="$next_image"
                     current_image_version="$image_version"
-                    out=$(docker stop "$migration_container" 2>&1) || {
+                    docker:container:stop "$migration_container" || {
                         err "Failed to stop the migration container $migration_container for $image_version:"
-                        printf "%s\n" "$out" | prefix "  ${GRAY}|${NORMAL} "
                         break 3
                     }
                     expected_stop="1"