Media API: Using context's classloader in MediaBrowser

When subscribing media updates, we allow users to pass options as
Bundles, in which users may put non-framework-defined parcelables,
which would cause ClassNotFoundException when media browser tries
to compare options to select the specified callback.

Sets any passed options' classloader as context's classloader to
solve the problem.

Test: manually checks if crashed APPs can survive after the fix
Bug: 62648808
Change-Id: I670c8da4ebc7845487db3a0d22c9d2baf727056f