parse out the v in the agent version (#3362)

api/server/shared/features/features.go

@@ -26,6 +26,11 @@ func isPorterAgentUpdated(agent *kubernetes.Agent, major, minor, patch int) bool
 		return true
 	}
 
+	if !strings.HasPrefix(tag, "v") {
+		return false
+	}
+
+	tag = strings.TrimPrefix(tag, "v")
 	parsedTag := strings.Split(tag, ".")
 	if len(parsedTag) != 3 {
 		return false