Fixed TSDB shipper GCS cli flags registration (#1807)

Signed-off-by: Marco Pracucci <[email protected]>

Author: pracucci

pkg/storage/tsdb/config.go

@@ -37,6 +37,7 @@ type Config struct {
 // RegisterFlags registers the TSDB flags
 func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
 	cfg.S3.RegisterFlags(f)
+	cfg.GCS.RegisterFlags(f)
 
 	f.StringVar(&cfg.Dir, "experimental.tsdb.dir", "tsdb", "directory to place all TSDB's into")
 	f.StringVar(&cfg.SyncDir, "experimental.tsdb.sync-dir", "tsdb-sync", "directory to place synced tsdb indicies")