Use StructNlAttr to handle struct nlattr

This is a no-op change to use the same structure to reduce the
code duplication.

Netlink lib provides the same structure for parsing the
attributes. Parsing attribute using StructNlAttr was also
applied in the code in the AutomaticOnOffKeepaliveTracker.
Align the design in two places.

Bug: 308737805
Test: atest NetworkStackTests
Test: use ss command to dump to socket status to confirm
Change-Id: I973db3a23bbe6dda0032c69e767fa69cd6f031d7
1 file changed