runtime: fix a gpgpu event and thread local gpgpu handling bug.

runtime: fix a gpgpu event and thread local gpgpu handling bug.

When pending a command queue, we need to record the whole gpgpu
structure not just the batch buffer. For the following reason:

1. We need to keep those private buffer, for example those printf buffers.
2. We need to make sure this gpgpu will not be reused by other enqueuement.

v2:
Don't try to flush all user event attached to the queue.
Just need to flush the current event when doing command queue flush.

Signed-off-by: Zhigang Gong <zhigang.gong@intel.com>
Reviewed-by: "Yang, Rong R" <rong.r.yang@intel.com>