fix: use updated fn-ps-is-app-running function to determine an application's status

In some cases, a single allocation for a service may not be running, but the others will, and `is_app_running` will return the wrong thing.

Closes #2772

plugins/ps/functions

@@ -91,10 +91,17 @@ ps_start() {
   declare desc="starts app"
   local APP="$1"; verify_app_name "$APP"
   local IMAGE_TAG=$(get_running_image_tag "$APP");
+  local RUNNING
 
   if (is_deployed "$APP"); then
     plugn trigger pre-start "$APP"
-    if ! (is_app_running "$APP"); then
+    RUNNING="$(fn-ps-is-app-running "$APP")"
+
+    if [[ "$RUNNING" == "mixed" ]]; then
+      dokku_log_warn "App is running in mixed mode, releasing"
+    fi
+
+    if [[ "$RUNNING" != "true" ]]; then
       release_and_deploy "$APP" "$IMAGE_TAG"
     else
       dokku_log_warn "App $APP already running"