revert commits that broke the storage BST and the nightly

Revert "CA-125122: Ensure the existance of remotepath when calling _isbind"

This reverts commit 6cf9efdef7984aec28e51f5a45f2ad3373fa3a8b.

Revert "CA-125137: sr_ref doesn't always exist"

This reverts commit f03332c3c82f1b9d893cf3328d6a166febd6e502.

Revert "CP-6697: normal ismount can not deal with bind mount"

This reverts commit eed0ec8f4b2fc01e97e49a1bd5913501b7b53c39.

Revert "CP-6697: Modernize FileSR as an independent SR type"

This reverts commit 34b9bb382e06ad952fb491446b47d65e6f64860d.

Revert "CP-6697: Refactor _checkmount to base class FileSR"

This reverts commit 691cd9782b28eccd5d6662b34ea8fae42c8cb6cb.

Revert "CP-6697: Fix FileSR capability config and param docs"

This reverts commit d80fe84f04be06db746ad0694ef90b4b0f1f86b5.

Revert "CP-6697: Add "nosubdir" flag for NFSSR"

This reverts commit 8eb8126f0e02284776b0989dd5c4e51eb446f941.

Revert "CP-6697: Add "coalesce" flag to SR other-config"

This reverts commit 3437a417b03ac6456ee9deab732c7b37e3980aa1.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>