SUNRPC: Fix sockaddr handling in svcsock_accept_class trace points

Avoid potentially hazardous memory copying and the needless use of
"%pIS" -- in the kernel, an RPC service listener is always bound to
ANYADDR. Having the network namespace is helpful when recording
errors, though.

Fixes: a0469f46 ("SUNRPC: Replace dprintk call sites in TCP state change callouts")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>