filecopy: cast perms string to oct

c95b33d0362f37caf10273efbcb06e0481a28eb7 dropped the call to oct() on
the file mode. The change was not called out in the release notes and
can break systems upgrading from older code. This restores the explicit
cast to octal before passing the file mode to LC::Check.

Closes #165
Merge pull request #166 from ned21/filecopy-mode-fix

filecopy: cast perms string to oct