fix Bundler patch in case gemfile is run multiple times

Change-Id: I544033693c8b9cdec16bf5ee31539c6f4904aafb
Reviewed-on: https://gerrit.instructure.com/30793
Reviewed-by: Brian Palmer <brianp@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

Gemfile

@@ -30,11 +30,13 @@ end
 require File.expand_path("../config/canvas_rails3", __FILE__)
 
 # patch bundler to do github over https
-class Bundler::Dsl
-  alias_method :_old_normalize_options, :_normalize_options
-  def _normalize_options(name, version, opts)
-    _old_normalize_options(name, version, opts)
-    opts['git'].sub!('git://', 'https://') if opts['git'] && opts['git'] =~ %r{^git://github.com}
+unless Bundler::Dsl.private_instance_methods.include?(:_old_normalize_options)
+  class Bundler::Dsl
+    alias_method :_old_normalize_options, :_normalize_options
+    def _normalize_options(name, version, opts)
+      _old_normalize_options(name, version, opts)
+      opts['git'].sub!('git://', 'https://') if opts['git'] && opts['git'] =~ %r{^git://github.com}
+    end
   end
 end