Refactor IssueUss class

[frankgiordano]

Changed IssueUss class name to UssCmd. This makes method API naming convention consistent with other packages.

In addition, internal refactoring resulting in the following benefits:

• No manual disconnect() calls cluttering the finally block.
• try-with-resources guarantees cleanup, even on exceptions.
• issueCommand method logic is now very focused: create resources → wait → return result.