Relax restrictions on load state

Allow indirect access to members (such as DRM engine, manifest, etc)
from Player methods as soon as they become available, instead of
waiting until the very end of the load process.

This fixes application access to several methods during the
"manifestparsed" event.  The point of the "manifestparsed" event was
to allow early access to manifest and other metadata before streaming
begins.

This also lays the foundations for improvements in native HLS support
in those same methods, including the ability to get track information.

Issue #382
Issue #997
Fixes b/131604508

Change-Id: Ifee7b06fc2ccdcf5bcdf1c44f2f851d1d7e67fa1