pfcp creates destination before assuring it can read source

[jti-lanl]

[Dave Bonnie mentioned this.] The result is that we get an error an leave a size-zero destination-file.

Should probably do an access(), or something, in process_stat_buffer(). If we can't read, then print a non-fatal error, and do not add the file to the copy list.

[jti-lanl]

Fixed. Also applies to deep compares, where source or destination is unreadable.