net: dst: Improve concurrency performance of dst_entry

JIRA: https://issues.redhat.com/browse/RHEL-15695
Tested: verified performance improvement with memcached/memtier_bench
with one thread per core each.

The patches improve the performance of parallel local connections.
Because the receive side of the connection is handled on the same cpu as
the data was sent for local connections, contention and false sharing
was observed between the sending core and the receiving core.

Signed-off-by: Felix Maurer fmaurer@redhat.com