tcp: rename functions for unlocking tcp connections

One function is used on restoring and one is used on dumping,
so each function has own prefix rst or cpt.
The both functions have the same effect, so the main part of the names
is same and it describes "unlock_tcp_connections".

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>