Dynamic disk configuration is not correctly provisioned

[vponomarev]

Hello.

seaweed-up have functions for dynamic disk configuration (func prepareUnmountedDisks), but this disks are not configured in volume server. Also, this info will not be passed to seaweed during next seaweed-up run.

My suggestion:

1. All dynamically created configuration is stored in separate .yaml file.
2. Content of this file is used during next run of seaweed-up
3. User can decide if he want to move params from dynamic to static config file or to leave it unchanged

I plan to implement such changes in nearest CR.

[chrislusf]

sounds good!