SDK / exoplayer

For now, just allow any prefix (and don't check the namespace).
Checking the namespace requires turning on the XmlPullParser
namespace awareness feature, but this can only be done before
parsing, and I think requires us to specify the namespace when
querying other attributes. This would also risk breaking services
who currently don't set namespaces correctly.

It's possible we'll run into similar issues with the few other
tags (e.g. mspr:pro). We should revisit enabling namespace
awareness if/when we see this.

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