Detect attempts to replace directory symlink to directory in package

Detect attempts to replace directory symlink to directory in package

- Rpm cannot currently *correctly* deal with directory symlink changing
  to a directory through updates, detect early and abort with conflicts
  instead of proceeding with known-broken results: previously these
  would seemingly succeed but without actually doing the requested
  changes, and leaving orphans on the disk. Far less evil than the
  directory replacement failure but incorrect anyway.
- Same %pretrans wackiness as with directory replacements applies here.
- Adjust test-suite to match the new behavior.
- It's possible there are packages that have been relying on the former
  broken "success" results, so this might need further fine-tuning...