(maint) Add logging when image pull fails

This commit adds logging to indicate that we fall back to assuming a
local version of the job image when pulling it from the remote fails.
This should help users recognize that the pull errors are red herrings
in air-gapped installs, and that the job will proceed, assuming the
image has been loaded into the runtime out of band.

Author: Magisus

tasks/run_cd4pe_job.rb

@@ -435,6 +435,10 @@ def update_container_image
       end
 
       @logger.log(result[:message])
+
+      if (result[:exit_code] != 0)
+        @logger.log("Unable to update image #{@container_image}, falling back to local image.")
+      end
     end
   end