Merge #11107: Fix races in AppInitMain and others with lock and atomic bools

Merge #11107: Fix races in AppInitMain and others with lock and atomic bools

c626dcb50 Make fUseCrypto atomic (MeshCollider)
731065b11 Consistent parameter names in txdb.h (MeshCollider)
35aeabec6 Make fReindex atomic to avoid race (MeshCollider)
58d91af59 Fix race for mapBlockIndex in AppInitMain (MeshCollider)

Pull request description:

  Fixes https://github.com/bitcoin/bitcoin/issues/11106

  Also makes fReindex atomic as suggested in @TheBlueMatt comment below, and makes fUseCrypto atomic as suggested in 10916

  https://github.com/bitcoin/bitcoin/pull/11107/commits/d291e7635b0ef4156c2805c6c4ee1adad91f0307 just renames the parameters in the txdb header file to make them consistent with those used in the cpp file, noticed it when looking for uses of fReindex

Tree-SHA512: b378aa7289fd505b76565cd4d48dcdc04ac5540283ea1c80442170b0f13cb6df771b1a94dd54b7fec3478a7b4668c224ec9d795f16937782724c5d020edd3a42