Replace u8string method to keep return value consistent (#2308) #2938

Job	Run time
env-protect-setup	7s
authorize	2s
get-dev-image / get-image	5s
code-coverage	11m 28s
clang-tidy	16m 15s
generate-matrix	2m 34s
build-and-test (BPF opt (4.14.254), kvm, --config=qemu-bpf --compilation_mode=opt --//bazel/test_...	2m 10s
build-and-test (ASAN, nokvm, --config=asan --compilation_mode=dbg, bazel_buildables_sanitizer, ba...	27m 34s
build-and-test (Clang opt + UI, nokvm, --config=clang --compilation_mode=opt, bazel_buildables_cl...	7m 23s
build-and-test (BPF opt (6.1.106), kvm, --config=qemu-bpf --compilation_mode=opt --//bazel/test_r...	2m 3s
build-and-test (Go race detector, nokvm, --config=go_race --compilation_mode=opt, bazel_buildable...	2m 55s
build-and-test (TSAN, nokvm, --config=tsan --compilation_mode=dbg, bazel_buildables_sanitizer, ba...	13m 55s
build-and-test (Clang debug, nokvm, --config=clang --compilation_mode=dbg, bazel_buildables_clang...	13m 1s
build-and-test (GCC opt, nokvm, --config=gcc --compilation_mode=opt, bazel_buildables_gcc_opt, ba...	6m 28s
build-and-test-status	3s
	1h 46m 3s

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