passthrough_ll: remove symlink fallbacks (#514)

passthrough_ll: remove symlink fallbacks (#514)

* passthrough_ll/hp: remove symlink fallbacks

Path lookup in the kernel has special rules for looking up magic symlinks
under /proc.  If a filesystem operation is instructed to follow symlinks
(e.g. via AT_SYMLINK_FOLLOW or lack of AT_SYMLINK_NOFOLLOW), and the final
component is such a proc symlink, then the target of the magic symlink is
used for the operation, even if the target itself is a symlink.  I.e. path
lookup is always terminated after following a final magic symlink.

I was erronously assuming that in the above case the target symlink would
also be followed, and so workarounds were added for a couple of operations
to handle the symlink case.  Since the symlink can be handled simply by
following the proc symlink, these workardouds are not needed.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Co-authored-by: Miklos Szeredi <mszeredi@redhat.com>