Fix vizier-pem DNS parser crash due to stack overflow and eventual segfault #3009

Job	Run time
env-protect-setup	6s
authorize	4s
get-dev-image / get-image	5s
generate-matrix	2m 55s
clang-tidy	15m 47s
code-coverage	-1s
build-and-test (BPF opt (4.14.254), kvm, --config=qemu-bpf --compilation_mode=opt --//bazel/test_...	24m 16s
build-and-test (Go race detector, nokvm, --config=go_race --compilation_mode=opt, bazel_buildable...	2m 57s
build-and-test (Clang opt + UI, nokvm, --config=clang --compilation_mode=opt, bazel_buildables_cl...	5m 23s
build-and-test (Clang debug, nokvm, --config=clang --compilation_mode=dbg, bazel_buildables_clang...	3m 18s
build-and-test (TSAN, nokvm, --config=tsan --compilation_mode=dbg, bazel_buildables_sanitizer, ba...	2m 51s
build-and-test (BPF opt (6.1.106), kvm, --config=qemu-bpf --compilation_mode=opt --//bazel/test_r...	32m 50s
build-and-test (ASAN, nokvm, --config=asan --compilation_mode=dbg, bazel_buildables_sanitizer, ba...	6m 7s
build-and-test (GCC opt, nokvm, --config=gcc --compilation_mode=opt, bazel_buildables_gcc_opt, ba...	3m 7s
build-and-test-status	3s
	1h 39m 48s

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