[#592] adm: Allow to tick epoch concurrently

Epoch can be ticked by IR in the background. Because the only usecase
for this is to apply some changes, the right behaviour is ignoring an
error, not retrying.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

cmd/frostfs-adm/internal/modules/morph/epoch.go

@@ -3,6 +3,7 @@ package morph
 import (
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/rpcclient/unwrap"
@@ -38,7 +39,14 @@ func forceNewEpochCmd(cmd *cobra.Command, _ []string) error {
 		return err
 	}
 
-	return wCtx.awaitTx()
+	if err := wCtx.awaitTx(); err != nil {
+		if strings.Contains(err.Error(), "invalid epoch") {
+			cmd.Println("Epoch has already ticked.")
+			return nil
+		}
+		return err
+	}
+	return nil
 }
 
 func emitNewEpochCall(bw *io.BufBinWriter, wCtx *initializeContext, nmHash util.Uint160) error {