Fix android.media.cts.MediaPlayerFlakyNetworkTest failure

Added mDisconnectLock to seperate it from mLock, used for protecting
mDataSource, mHttpSource and mDisconnected in order that disconnect()
won't be blocked by mLock.

Bug: 133900877
Test: android.media.cts.MediaPlayerFlakyNetworkTest
Change-Id: I15693c0a61f898aad4035d0fa55c8af25de4fc96
2 files changed