destroy_wait doesn't store all RPC clients. There was a list named
"all_clients" above it, which got moved to struct sunrpc_net in 2012,
but the comment was never removed.

Fixes: 70abc49b ("SUNRPC: make SUNPRC clients list per network namespace context")
Signed-off-by: Siddh Raman Pant <siddh.raman.pant@oracle.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>