Fix failing test in MySQL.

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

activerecord/test/cases/associations/belongs_to_associations_test.rb

@@ -34,8 +34,13 @@ def test_belongs_to_with_primary_key
 
   def test_belongs_to_with_primary_key_joins_on_correct_column
     sql = Client.joins(:firm_with_primary_key).to_sql
-    assert_no_match /"firm_with_primary_keys_companies"\."id"/, sql
-    assert_match /"firm_with_primary_keys_companies"\."name"/, sql
+    if current_adapter?(:MysqlAdapter)
+      assert_no_match /`firm_with_primary_keys_companies`\.`id`/, sql
+      assert_match /`firm_with_primary_keys_companies`\.`name`/, sql
+    else
+      assert_no_match /"firm_with_primary_keys_companies"\."id"/, sql
+      assert_match /"firm_with_primary_keys_companies"\."name"/, sql
+    end
   end
 
   def test_proxy_assignment
@@ -457,7 +462,7 @@ def test_invalid_belongs_to_dependent_option_nullify_raises_exception
       Author.belongs_to :special_author_address, :dependent => :nullify
     end
   end
-  
+
   def test_invalid_belongs_to_dependent_option_restrict_raises_exception
     assert_raise ArgumentError do
       Author.belongs_to :special_author_address, :dependent => :restrict