Don't use sp<>&

because they may end up pointing to NULL after a NULL check was performed.

Bug: 28166152
Change-Id: Iab2ea30395b620628cc6f3d067dd4f6fcda824fe

status_t MediaPlayer::reset()
{
    ALOGV("reset");
 Mutex::Autolock _l(mLock);
 return reset_l();
}

status_t MediaPlayer::reset()
{
    ALOGV("reset");
 Mutex::Autolock _l(mLock);
 return reset_l();
}
