diag: dci: Prevent task deallocation and possible resource leak

Prevent DCI clients' task structs from being deallocated to provide
diag driver a chance to clean up its dci client list. Also update
dci client list pid reference count properly to prevent any resource
leakage.

Bug: 68726653
Change-Id: I31c61442a48ac263fd9ff341f6c29db8ace90952
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>