Removed check for dst existence in file copy.

This was carried over from moving the link copy code from backup checks.
dst existence should not be checked. To be lighter on volumes where
writes are slow or expensive, this should do a hash collision check
first to compare the files.
Fixed bug in dircopy with unassigned var.

DirCopies referenced a variable before assignment due to a mistake
refactoring to separate dir creation from file copies. Caused a crash
failure when triggered.
Merge branch 'bugfix/copy-failure' into dev