NFSv4.x: Fail client initialisation if state manager thread can't run

[ Upstream commit b4e4f66901658fae0614dea5bf91062a5387eda7 ]

If the state manager thread fails to start, then we should just mark the
client initialisation as failed so that other processes or threads don't
get stuck in nfs_wait_client_init_complete().

Reported-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Fixes: 4697bd5e ("NFSv4: Fix a race in the net namespace mount notification")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>