CBG-4518: better error to pass up stack when xattr config doesn't exist

[gregns1]

CBG-4518

• Pass up stack more descriptive error when metadata doc is found with no xattr config
• Added test to test different scenarios returning the new xattr error type added
• Added code to add db's ties to a bucket into invalid db tracking map when we hit this issue on config poll for a bucket.
• Added code to fail config update and take tb offline, avoiding a config rollback when this is hit during a db config update.

Pre-review checklist

• Removed debug logging (fmt.Print, log.Print, ...)
• Logging sensitive data? Make sure it's tagged (e.g. base.UD(docID), base.MD(dbName))
• Updated relevant information in the API specifications (such as endpoint descriptions, schemas, ...) in docs/api

Integration Tests

• GSI=true,xattrs=true https://jenkins.sgwdev.com/job/SyncGateway-Integration/2966/

[torcolvin]

I feel pretty nervous about changing this error still, given how the retry code works here

sync_gateway/rest/config_manager.go

Line 375 in aaa9f01

if legacyErr != nil && !base.IsDocNotFoundError(legacyErr) {

I'd make sure that we have tests in the rest package that cover each of the places IsDocNotFoundError where the error would be hit in config_manager for xattr config.

I think we should pursue writing a document describing the ways that a user can end up this scenario.

[torcolvin]

It is not clear that this is the correct solution for this problem overall. This adds complexity to server context and might not solve the original problem.

This probably won't be merged as is, and rethinking the problem and deciding if this right approach is correct. It may be that this is OK, but this ticket is not a current priority so closing this PR. This can be considered parked, and reopened when we next work on this ticket.