RDS: use c_wq for all activities on a connection

RDS: use c_wq for all activities on a connection

RDS connection work, send work, recv work etc events have been
serialised by use of a single threaded work queue. For loopback
connections, we created a separate thread but only connection
work is moved on it. This actually under utilises the thread
and creates un-necessary contention for send/recv work and
connection work for loopback connections.

We move remainder loopback work as well on the rds_local_wq
which garantees serialisation as well as delinks the loopback
and non loopback work(s).

Orabug: 22347191

Tested-by: Michael Nowak <michael.nowak@oracle.com>
Tested-by: Rafael Alejandro Peralez <rafael.peralez@oracle.com>
Tested-by: Liwen Huang <liwen.huang@oracle.com>
Tested-by: Hong Liu <hong.x.liu@oracle.com>
Reviewed-by: Mukesh Kacker <mukesh.kacker@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>