logfix:print warn instead of error when dir not found. #1473

Job	Run time
tests (vmm/sandbox, --all-features)	3m 43s
checks (vmm/sandbox, --all-features)	5m 2s
checks (vmm/task, --all-features)	4m 27s
checks (shim, --all-features)	4m 11s
tests (vmm/task, --all-features)	3m 24s
checks (quark, --all-features)	4m 19s
tests (shim, --all-features)	2m 33s
checks (runc, --all-features)	4m 29s
tests (quark, --all-features)	2m 27s
checks (wasm, --features=wasmedge, 0.13.5)	5m 2s
tests (runc, --all-features)	3m 2s
checks (wasm, --features="wasmedge, wasmedge_wasi_nn", 0.13.5)	4m 51s
checks (wasm, --features=wasmtime)	4m 45s
tests (wasm, --features=wasmedge, 0.13.5)	3m 10s
tests (wasm, --features=wasmtime)	3m 46s
	59m 11s

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