Deserialization old containers on decryption fail

[Zhaars]

Acra should return pure old container as is in case of decryption failure. Currently, on newly found old container(AcraStruct/AcraBlock) Acra serialize it to general container to get corresponded handler during decryption, but in case of failure return general container which is not correct.

Note: Acra should return deserialized container only in case of pure AcraStruct/AcraBlock, in all other scenarios general container should be returned.

Checklist

• Change is covered by automated tests
• The coding guidelines are followed
• Public API has proper documentation in the Acra documentation site or has PR on documentation repository
  with new changes
• CHANGELOG.md is updated (in case of notable or breaking changes)
• CHANGELOG_DEV.md is updated
• Benchmark results are attached (if applicable)
• Example projects and code samples are up-to-date (in case of API changes)