envutil.rb: do not check RSS by default

* test/ruby/envutil.rb (Test::Test#assert_no_memory_leak): do not
  check RSS by default, enabled by rss optional keyword argument.
  TestHash#test_exception_in_rehash sometimes fails otherwise.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45314 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_hash.rb: refine a test

* test/ruby/test_hash.rb (test_exception_in_rehash): do not run twice
  since this test does not use @cls.  making a hash may increase
  memory usage and should be in preparation.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45315 b2dd03c8-39d4-4d8f-98ff-823fe69b080e