GenericSource: reset mDrmManagerClient when mDataSource is cleared. am: 224858e719 am: 69c8e36da7 am: 3fcddfd23a am: e01ba47052 am: adadada4f0 am: ddb3d77dad
am: 301a55c115

* commit '301a55c1152949f6c06247a2044f98cd150fcfde':
  GenericSource: reset mDrmManagerClient when mDataSource is cleared.