Support amazonlinux via http text/plain (#850)

scan/serverapi.go

@@ -664,6 +664,10 @@ func ViaHTTP(header http.Header, body string) (models.ScanResult, error) {
 		osType = &centos{
 			redhatBase: redhatBase{base: base},
 		}
+	case config.Amazon:
+		osType = &amazon{
+			redhatBase: redhatBase{base: base},
+		}
 	default:
 		return models.ScanResult{}, xerrors.Errorf("Server mode for %s is not implemented yet", family)
 	}