SUNRPC: RPC level errors should set task->tk_rpc_status

[ Upstream commit ed06fce0b034b2e25bd93430f5c4cbb28036cc1a ]

Fix up a case in call_encode() where we're failing to set
task->tk_rpc_status when an RPC level error occurred.

Fixes: 9c5948c2 ("SUNRPC: task should be exit if encode return EKEYEXPIRED more times")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>