fix h2 rpc_dump mem leak bug (#2661) #1

Job	Run time
clang-compile-with-cmake	2m 45s
clang-compile-with-bazel	14m 15s
clang-compile-with-boringssl	20m 4s
clang-compile-with-bazel-all-options	17m 3s
clang-compile-with-cmake-all-options	4m 39s
clang-compile-with-make	2m 37s
clang-compile-with-make-all-options	4m 43s
gcc-compile-with-bazel	16m 27s
clang-unittest	14m 30s
gcc-compile-with-bazel-all-options	19m 3s
gcc-compile-with-cmake	3m 23s
gcc-compile-with-cmake-all-options	5m 4s
gcc-compile-with-boringssl	20m 25s
gcc-compile-with-make	2m 57s
gcc-compile-with-make-all-options	5m 1s
	2h 32m 56s

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