Add missing init calls in buffer tests in 1.0.1

These tests are asynchronous, but didn't call waitUntilDone correctly in
1.0.1 when run under the webkit test runner. Add the missing call. In
1.0.2+, waitUntilDone is called indirectly and no changes are needed.
Merge pull request #372 from NVIDIA/buffer-test-init

Add missing init calls in buffer tests in 1.0.1