update OPIC cache hook to also flush image style when refreshing images

See https://www.pivotaltracker.com/story/show/188143806

Addition of code to flush image styles of cached OPIC images when refreshing the base image. Without this, there is a disconnect between the main image and derivative image styles.

added Module Updates label

assigned to @canini.16

approved this merge request

Looks good to me:)

merged

mentioned in commit f298cb58