vcl: fix vcl issue in multi-thread-workers mode

vcl: fix vcl issue in multi-thread-workers mode

   In some multi-process/thread applications, a connection FD
is created on main process and actual data processing is done
in worker process. The main process does nothing. For such
applications, when multi-thread-workers is enabled, in current
VLS code, the session events are still enqueued to the VCL
worker corresponding to Main process. As the main process is
not dequeuing any event, application doesn't move forward.
This patch fixes this issue by enabling VCL worker
corresponding to the Worker process as listener of the session.

Type: improvement

Signed-off-by: Mohamed Feroz <[email protected]>
Change-Id: Ia7e6270c1acbce7feeafbf281c661285d63c3b22