Make Gitaly configuration immutable and local

The Gitaly config.Cfg is a global mutable construct that abstracts away the state of the Gitaly configuration file. It has been the root of a number of race conditions. There are times where a test needs to add/remove storages to test a feature, and this can cause race conditions due to the concurrency inherent in a Gitaly server.

Since the contents of the file do not change once Gitaly starts, there is no need for the construct to be mutable. Whenever a test or server needs access to the configuration file, an immutable copy of the construct is preferable to prevent these race conditions from occurring.

Each service should get a dependency injected deep copy of the configuration file so that the configuration state is unable to change once the service starts.

• objectpool service
• repository service
• commit service
• diff service
• hook service the dependent code gone
• objectpool
• remote
• smarthttp
• ssh
• wiki
• namespace ...