Revert "libbootloader_message: use different fstab paths for normal/recovery boot"

This reverts commit 37bd4417.

The logic here is better to be moved into fs_mgr, not fs_mgr clients.

Bug: 35811655
Bug: 36502022

Change-Id: Iae79bd8f7131516ad223f3323f1bc1d805206d51
Test: normal boot sailfish, go to Settings > System & tap 
      on "Factory Data reset"
Test: recovery boot sailfish