granulate-utils: Fix resolve_proc_root_links

[netaneld122]

Fix resolve_proc_root_links handling of links that resolve to sub-path links.

Example:

{tmpdir}/link
    link -> {tmpdir}/a/c
    a -> {tmpdir}/b
Eventually we expect {tmpdir}/link to resolve to {tmpdir}/b/c

[Jongy]

Didn't review yet, but just one note - there are several tests in gprofiler which test this function's behavior. Please create a PR in gprofiler which points to this commit so the tests run agains this commit. (Plus, post merging we'll want to update gprofiler as well).

[Jongy]

The core change is clear and looks good to me. I gave 2 nitpick comments. @michelhe as this is a very core part, please review as well.

[michelhe]

Looks good, 1 small comment and a question -
Wouldn't nsentring to the process mount namespace and then simply readlink() inside the namespace will serve the same purpose, but we'll have the OS do the resolving for us?