[#968] adm: Allow concurrent epoch ticks

Previous fix was incomplete, there are two possible places for this
error to occur.

Refs #592

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

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

@@ -37,18 +37,14 @@ func forceNewEpochCmd(cmd *cobra.Command, _ []string) error {
 		return err
 	}
 
-	if err := wCtx.sendConsensusTx(bw.Bytes()); err != nil {
-		return err
+	if err = wCtx.sendConsensusTx(bw.Bytes()); err == nil {
+		err = 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
+	if err != nil && strings.Contains(err.Error(), "invalid epoch") {
+		cmd.Println("Epoch has already ticked.")
+		return nil
 	}
-	return nil
+	return err
 }
 
 func emitNewEpochCall(bw *io.BufBinWriter, wCtx *initializeContext, nmHash util.Uint160) error {