Fix unsafe container cleanup in delete_image

Previously, delete_image stopped ALL containers on the system before
removing test images, which could disrupt unrelated containers.

Changes:
- Only stop and remove containers created from the specific test image
- Match containers using substring comparison to handle sha256: prefix
- Check container state before stopping to avoid unnecessary operations
- Handle NotModifiedError for already-stopped containers

This makes the test suite safe to run on development machines where
other Docker containers may be running.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

Author: chorrell

spec/spec_helper.rb

@@ -15,9 +15,21 @@ def create_image(version)
 
   def delete_image
     puts "Deleting image..."
-    # Stop all containers so we can remove the image
-    for container in Docker::Container.all(:all => true)
-      container.stop
+    # Stop and remove only containers created from this image
+    Docker::Container.all(:all => true).each do |container|
+      container_image = container.info['Image']
+      container_image_id = container.info['ImageID']
+      
+      # Match image IDs - container IDs may have sha256: prefix and be full hashes
+      # while @image.id is the short ID
+      if container_image&.include?(@image.id) || container_image_id&.include?(@image.id)
+        begin
+          container.stop unless container.info['State'] == 'exited'
+          container.delete(:force => true)
+        rescue Docker::Error::NotModifiedError
+          # Container already stopped, ignore
+        end
+      end
     end
 
     @image.remove(:force => true)