Refine missing mount options in the .config file

[xiaogaozi]

What would you like to be added:

Add more mount options to .config file, e.g. --backup-meta.

Why is this needed:

Instead of using the ps command, users can view all mount options uniformly in the .config file.

[SandyXSD]

Other options requiring discussions:

• log
• metrics
• consul
• usage-report
• syslog
• o (extra FUSE options)
• enable-xattr
• bucket (will be reset to the value of that in format, which might be different)
• io-retries (not work for now: The --io-retries option doesn't seem to work correctly #1413)

[davies]

File .config is provided for debug, not a public interface for end users, so we don't have a plan to expose all the configurations in it, close it for now.