rpc server: fix host filter for localhost on ipv6 #5738

Job	Run time
preflight / preflight	41s
preflight / ci-versions	1m 33s
test-full-crypto-feature	2m 53s
test-frame-ui	46m 58s
cargo-check-benches (master)	21m 36s
test-node-metrics	11m 13s
cargo-check-benches (current)	24m 4s
cargo-check-all-crate-macos	12m 3s
cargo-check-each-crate (1)	20m 4s
cargo-check-each-crate (2)	23m 16s
cargo-check-each-crate (3)	9m 51s
cargo-check-each-crate (4)	21m 37s
cargo-check-each-crate (5)	28m 8s
cargo-check-each-crate (6)	15m 21s
cargo-check-each-crate (7)	28m 31s
test-frame-examples-compile-to-wasm	3m 4s
test-deterministic-wasm	6m 31s
check-tracing	2m 29s
check-metadata-hash	6m 17s
node-bench-regression-guard	13s
All test misc tests passed	1s
	4h 46m 24s

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