* Fix caching issue of storage blob config blob
* Add tests to ensure retention is set during config
Ensure retention is properly set when either changing retention options
or initializing the repo with retention.
* implemented format blob cache abstraction
* moved upgrade lock logic to repo/format
* moved set parameters logic to repo/format
* moved change password functionality to repo/format
* mechanical changes
* mechanical changes to react to format manager interface
* get current repository format bytes instead of static
* implemented format.Manager which dynamically fetches and caches latest format blob
* repo changes to use format.Manager
* fixed failing unit test due to different timings
* reduced lock contention by using RWMutex
* serve immutable parts of format without any locks
* increase test timeout
* fixed handling of negative validDuration
The new rules are:
- validDuration < 0 - ignore initial cached file, refresh every 15min
- validDuration > 15min - refresh every 15 minutes
- validDuration > 0 && validDuration <= 15min - refresh using provided
interval (mostly used for testing)
