e_policy_visibility: do not remove vc->buf_attach event handler while executing pende...

e_policy_visibility: do not remove vc->buf_attach event handler while executing pended job

There was an issue that the E_Vis_Grab resource which was wating for buffer attach event
couldn't freed if the E_Vis_Grab's timer was expired.
This resource would be freed when the E_Client was destroyed.
However, if the E_Client is not destroyed, then the memory can be increased continuousely.

This patch makes the E_Vis_Grab resource to be freed when a timeout is occured.

Change-Id: Ia6a1bee0ddeddaef42a52bd384ba50d027033827