Fix potential memory leak in SomeArgs

When recycling SomeArgs in pool, some fields are not set to null.
Which result potential memory leak as SomeArgs in pool still holds
the reference object.
To fix this issue, clear all args when recycling.

Change-Id: Ie730c3889da948c60ef746ddbe2e926d94ad7e06
Signed-off-by: Bin Chen <bin0515@gmail.com>
Signed-off-by: Wei Huang <hwbest.v@gmail.com>