test: Clean up randomly-named temporary images after testing
test: Clean up randomly-named temporary images after testing

 * This prevents accumulation of "aiodocker-xxxxx" images on your
   development system.

 * But it also skips this clean-up process in the CI server for
   fast shutdown.

gaopeiliang/aiodocker,barrachri/aiodocker,paultag/aiodocker,barrachri/aiodocker,gaopeiliang/aiodocker,gaopeiliang/aiodocker,barrachri/aiodocker