fix(azure-storage): keep queue metadata and table ACLs on ARM PATCH, list queue metadata, tolerate concurrent creates

[NitinKumar004]

Follow-ups from the #1541 review:

• ARM PATCH of a queue without metadata kept nothing and cleared it; it now leaves metadata alone. Same for a table's signedIdentifiers on PATCH. PUT still replaces.
• The ARM queue list now includes each queue's properties.metadata.
• Two concurrent PUTs for the same queue or table no longer return 409 to the second caller; it updates the queue/table the first one created.

Tested: go test ./server/azure/ ./server/azure/storageaccount/ (new TestARMQueuePatchKeepsMetadata), lint clean.