Allow disabling consistency checks in FetchRemote and CreateRepositoryFromURL

Geo uses both FetchRemote and CreateRepositoryFromURL to create the repository replicas. These RPCs perform consistency checks via git-fsck(1) to verify that received objects are sane. If the source repository has objects that don't pass verification (e.g. due to historic reason), then Geo would be unable to replicate such repository. This is unintended as the resulting replicas should ideally be exact copies of the source repository.

We should add options to both FetchRemote and CreateRepositoryFromURL that allows the caller to disable the consistency checks. This would both address the issue of failing replication as well as result in a speedup.