RDS: make the rds_{local_}wq part of rds_connection

RDS: make the rds_{local_}wq part of rds_connection

Instead of sprinkling if/else for loopback all over the place,
lets just add c_wq as part of rds_connection. This will prevent
missing cases like 'commit edca33be359c ("RDS: move more queing for
loopback connections to separate queue"), 'commit 8502173071b6
("rds: schedule local connection activity in proper workqueue")
or any future changes.

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>