NFSD: Keep existing listeners on portlist error

stable inclusion
from stable-5.10.76
commit 0f4308a164a9de4ffaf86b22082dbdfa16bdc601
bugzilla: 182988 https://gitee.com/openeuler/kernel/issues/I4IAHF

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f4308a164a9de4ffaf86b22082dbdfa16bdc601



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[ Upstream commit c2010694 ]

If nfsd has existing listening sockets without any processes, then an error
returned from svc_create_xprt() for an additional transport will remove
those existing listeners.  We're seeing this in practice when userspace
attempts to create rpcrdma transports without having the rpcrdma modules
present before creating nfsd kernel processes.  Fix this by checking for
existing sockets before calling nfsd_destroy().

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>

Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>