Make the tapping already there step actually work

For when the symlink for a tap already exists and points to the thing we are about to symlink. This can happen, mostly because my code has sucked, but since the filesystem can be edited by the user at whim, it's possible then too.

Library/Homebrew/cmd/tap.rb

@@ -34,7 +34,7 @@ def link_tap_formula formulae
         to = HOMEBREW_LIBRARY.join("Formula/#{formula.basename}")
 
         # Unexpected, but possible, lets proceed as if nothing happened
-        formula.delete if to.symlink? and to.realpath == from
+        to.delete if to.symlink? and to.realpath == from
 
         # using the system ln is the only way to get relative symlinks
         system "ln -s ../Taps/#{formula} 2>/dev/null"