Revert "tar: replace ad-hoc split functions with Re_str.split"

The ocaml-re librabry is found to be not thread safe. Removing all calls to the library

This reverts commit 44d5129e8491ad0ea5f956f5ea444aa09d2a5e90.

Signed-off-by: Akshay <akshay.ramani@citrix.com>