Bluetooth: Defer connection-parameter removal when unpairing

Systematically removing the LE connection parameters and autoconnect
action is inconvenient for rebonding without disconnecting from
userland (i.e. unpairing followed by repairing without
disconnecting). The parameters will be lost after unparing and
userland needs to take care of book-keeping them and re-adding them.

This patch allows userland to forget about parameter management when
rebonding without disconnecting. It defers clearing the connection
parameters when unparing without disconnecting, giving a chance of
keeping the parameters if a repairing happens before the connection is
closed.

Signed-off-by: Alfonso Acosta <fons@spotify.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>