rds: find connection drop reason

rds: find connection drop reason

This patch attempts to find connection drop details.

Rational for adding this type of patch is, there are too many
places from where connection can get dropped.
And, in some cases, we don't have any idea of the source of
connection drop. This is especially painful for issues which
are reproducible in customer environment only.

Idea here is, we have tracker variable which keeps latest value
of connection drop source.
We can fetch that tracker variable as per our need.

Orabug: 22631108

Signed-off-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Acked-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>