Update job_image_scan and ci_linter to allow job deletion
Context
Both jobs_image_scan
and ci_linter
jobs compare changes in jobs related files between the latest
branch and the current commit in an MR.
If a job is deleted, both jobs are trying to access those files, and it fails at the files didn't exist anymore
Objective
Change the behavior of both jobs to check if the changed files exist in the current commit. If not, don't perform further operations.