modify file updated timestamp handling for symlinks and taglinks

[Omarabdul3ziz]

Description

On the tf-autobuilder / v* view page, the "Updated" column shows the timestamp of the target flist file instead of the link's own modification time for symlinks and taglinks. This causes confusion because:

• When a new build is made (which happens on each merge), the target flist's timestamp gets updated
• The link's timestamp in the UI updates even though the link itself wasn't modified
• For example, a tag link created on Nov 19 shows Nov 20 (the timestamp of the flist inside) instead of Nov 19 (when the link was actually created)
  

Solution

Modified the frontend to display linktime (the link's modification time) instead of updated (the target file's modification time) for symlinks and taglinks.

[maxux]

LGTM