Fix a bug in ReFitLevel() where `FileMetaData::being_compacted` is not cleared #2758

Job	Run time
build-linux-cmake-with-folly	27m 44s
check-format-and-targets	23s
build-linux	16m 47s
build-linux-cmake-mingw	12m 34s
build-linux-cmake-with-benchmark	19m 25s
build-linux-cmake-with-folly-coroutines	32m 26s
build-linux-cmake-with-folly-lite-no-test	7m 47s
build-linux-encrypted_env-no_compression	15m 24s
build-linux-make-with-folly	28m 0s
build-linux-make-with-folly-lite-no-test	9m 19s
build-linux-release	14m 4s
build-examples	10m 28s
build-fuzzers	8m 29s
build-linux-clang10-asan	16m 59s
build-linux-clang10-clang-analyze	16m 55s
build-linux-clang10-ubsan	16m 27s
build-linux-clang-no_test_run	12m 13s
build-linux-clang-13-no_test_run	7m 2s
build-linux-gcc-11-no_test_run	10m 25s
build-linux-gcc-8-no_test_run	8m 43s
build-linux-gcc-10-cxx20-no_test_run	9m 19s
build-linux-mini-crashtest	30m 13s
build-linux-release-rtti	12m 12s
build-linux-unity-and-headers	13m 30s
build-linux-arm	14m 37s
build-linux-clang10-mini-tsan	24m 10s
build-linux-java	15m 14s
build-linux-java-pmd	13m 8s
build-linux-java-static	11m 47s
build-linux-static_lib-alt_namespace-status_checked	18m 42s
build-macos	17m 47s
build-macos-cmake (true)	40m 39s
build-macos-java	20m 50s
build-macos-java-static	21m 27s
build-macos-cmake (false)	36m 54s
build-macos-java-static-universal	26m 22s
build-windows-vs2019	53m 21s
	11h 11m 46s

Provide feedback