The function `setup_TCP_server_socket` (defined in img-remote.c) and
`setup_tcp_server` (defined in util.c) have very similar functionality.

Replace setup_TCP_server_socket() with setup_tcp_server() to reduce
code duplication and to enable IPv6 support for the image-cache action
of CRIU.

We set SO_REUSEADDR flag to allow reuse of local addresses.
Signed-off-by: Radostin Stoyanov <rstoyanov1@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>