CurlDownloadStrategy: remove "tarball_path" accessor

This information is already exposed as "cached_location", which is
common to all download strategies.

Library/Contributions/cmd/brew-mirror-check.rb

@@ -9,14 +9,13 @@ class Formula
 
     # Force the downloader to attempt the download by removing the tarball if
     # it is allready cached.
-    tarball_path = downloader.tarball_path
-    tarball_path.unlink if tarball_path.exist?
+    cached_download.unlink if cached_download.exist?
 
-    fetched = downloader.fetch
+    downloader.fetch
   rescue StandardError
     opoo "Failed to fetch from URL: #{url}"
   else
-    verify_download_integrity fetched if fetched.kind_of? Pathname
+    verify_download_integrity(cached_download) if cached_download.file?
   end
 end
 

Library/Homebrew/download_strategy.rb

@@ -31,7 +31,6 @@ class AbstractDownloadStrategy
 end
 
 class CurlDownloadStrategy < AbstractDownloadStrategy
-  attr_reader :tarball_path
   attr_accessor :local_bottle_path
 
   def initialize name, package