Refresh dump file modify timestamp before cleanup call (sonic-net#3595)

During the show techsupport, generate_dump calls techsupport_cleanup with current generated file. The techsupport_cleanup verifies the file path provided for file last modification timestamp and on success only proceeds to cleanup. It expects the file to be modified within last 20 secs. Sometimes when file is big, gzip takes more that 20 sec. Due to this, the last modify timestamp to current time stamp diff is greater than 20 and verify_recent_file_creation fails causing cleanup to fail.

How I did it
touch the tarfile after finishing the gzip to refresh modify timestamp.

How to verify it
run show techsupport

scripts/generate_dump

@@ -2223,6 +2223,9 @@ finalize() {
         else
             echo "WARNING: gzip operation appears to have failed." >&2
         fi
+        # sometimes gzip takes more than 20 sec to finish, causing file time create validation
+        # to fail. touching the tarfile created to refresh modify time.
+        touch ${TARFILE}
     fi
 
     # Invoke the TechSupport Cleanup Hook