Repeated captureSamples calls register unexpected behavior

Repeated calls to alcCaptureSamples without stopping audio capture, result in garbled reading of audio on all but the first call.

**Reproducibility:** A sample code exhibiting the issue can be found at [gist](https://gist.github.com/krunal-shah/570738c428dd822feafff4e29e1a57e6). The description of reproducing the issue can be found at the top of the sample code. It can be compiled and run using
1. `emcc -lopenal bug_sample.cpp -o bug_sample.html`
2. `python -m SimpleHTTPServer 8080`
3. Visit `localhost:8080/*path to bug_sample.html*`

**Details:** A doc describing the bug in detail, possible reason for the bug and a potential solution can be found at [doc](https://docs.google.com/document/d/10qJR_-itwlsb0VMAN84sCjbVOF99ZA-5yYcKlgv_cig/edit?usp=sharing).