[Refactor] Use JoinHostPort instead of fmt.Sprintf("%s:%d", host, port)

[robertdunlap-servicenow]

Go‑Lang’s best practices point out that using net.JoinHostPort will reduce the chances of bugs within the application.

Feature Suggestion

Use of JoinHostPort over fmt.Sprintf(..) to manually join hostname and port combinations.

Possible Implementation

Review all manually combined hostnames and ports, and where possible use Go‑Lang best practices, by
replacing fmt.Sprintf(..) with the recommended net.JoinHostPort.

Affected Files

/agent/sockets.go
/agent/api.go
/agent/statsd_server.go
/backend/agentd/agentd.go
/backend/dashboardd/dashboardd.go
/backend/pipelined/handle.go
/util/url/url.go

Context

No specific security risk in the current use of manually combining the hostname and port, but using of Go-Lang library might prevent an subtle issue in the future that is unseen. Reference to golang/go#28308