Rename all_the_rest.dart to all_the_rest_test.dart.

So that it will be run by the buildbots.

Also fix a bug which would have caused the test
'DirectoryBasedDartSdkTest.getSdkVersion' to fail when run by the
buildbots.

R=scheglov@google.com

Review URL: https://codereview.chromium.org//762823003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42068 260f80e4-7a28-3924-810f-c04153c831b5