vmm: fix clippy warning #1113

Job	Run time
checks (vmm/sandbox, --all-features)	4m 42s
tests (vmm/sandbox, --all-features)	3m 32s
checks (vmm/task, --all-features)	3m 57s
tests (vmm/task, --all-features)	2m 45s
tests (shim, --all-features)	2m 33s
checks (shim, --all-features)	3m 49s
tests (quark, --all-features)	2m 27s
checks (quark, --all-features)	3m 55s
tests (runc, --all-features)	2m 32s
checks (runc, --all-features)	4m 13s
tests (wasm, --features=wasmedge, 0.13.5)	2m 44s
checks (wasm, --features=wasmedge, 0.13.5)	4m 12s
tests (wasm, --features=wasmtime)	3m 30s
checks (wasm, --features=wasmtime)	4m 26s
	49m 17s

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