Revert "tcp: disallow bind() to reuse addr/port"

Revert "tcp: disallow bind() to reuse addr/port"

[ Upstream commit 3e8c806a08c7beecd972e7ce15c570b9aba64baa ]

This reverts commit c191a836a908d1dd6b40c503741f91b914de3348.

It causes known regressions for programs that expect to be able to use
SO_REUSEADDR to shutdown a socket, then successfully rebind another
socket to the same ID.

Programs such as haproxy and amavisd expect this to work.

This should fix kernel bugzilla 32832.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>