AutoObj/ThreadUtils: add AutoMutexUnlock for local unlock/auto-relock blocks
Typical usage:
AutoMutex l = m_cam->lock();
if (m_state != Idle)
THROW_HW_ERROR(InvalidValue) << "Camera not Idle";
m_state = Starting;
{
AutoMutexUnlock u(l);
m_cam->putCmd("status start");
}
m_state = Running;
m_cond.broadcast();