SUNRPC: Don't let RPC_SOFTCONN tasks time out if the transport is connected

mainline inclusion
from mainline-5.1-rc3
commit d84dd3fb
category: bugfix
bugzilla: 51818
CVE: NA

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If the transport is still connected, then we do want to allow
RPC_SOFTCONN tasks to retry. They should time out if and only if
the connection is broken.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Conflicts:
	net/sunrpc/clnt.c
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>