[yugabyte#9430] docdb: Added success message for all tablets and sing…

…le tablet compaction/flushes

Summary:
There was no notification for completion of all tablets compaction previously.
This PR adds print statements following the completion of compaction + flushes for single tablet and all tablets.

Test Plan:
- Jenkins
- When using `yb-ts-cli` for compactions/flushes, there should now be a success message:
```
>>> bin/yb-ts-cli --server_address=127.0.0.1:9100 compact_all_tablets
Successfully compacted all tablets
>>> bin/yb-ts-cli --server_address=127.0.0.1:9100 flush_all_tablets
Successfully flushed all tablets
>>> bin/yb-ts-cli --server_address=127.0.0.1:9100 flush_tablet 6ad60a8aa2d44e3aa4de8ad6976c6cd0
Successfully flushed tablet <6ad60a8aa2d44e3aa4de8ad6976c6cd0>
>>> bin/yb-ts-cli --server_address=127.0.0.1:9100 compact_tablet 6ad60a8aa2d44e3aa4de8ad6976c6cd0
Successfully compacted tablet <6ad60a8aa2d44e3aa4de8ad6976c6cd0>
```
Verify that failure messages still work:
```
>>> bin/yb-ts-cli --server_address=127.0.0.1:9100 compact_tablet invalid-tablet-id
Unable to compact tablet: IO error (yb/tools/ts-cli.cc:470): Failed to flush tablet: : code: TABLET_NOT_FOUND status { code: NOT_FOUND message: "Tablet not found: invalid-tablet-id" source_file: "../../src/yb/tserver/ts_tablet_manager.cc" source_line: 1637 errors: "\000" }
```

Reviewed By: jhe

Differential Revision: https://phabricator.dev.yugabyte.com/D12398

CONTRIBUTORS.md

@@ -139,3 +139,4 @@ This is a list of people who have contributed code to the [YugabyteDB](https://g
 * [jackstenglein](https://github.com/jackstenglein)
 * [BozhiYou](https://github.com/bozhiyou)
 * [pkj415](https://github.com/pkj415)
+* [leeleeian](https://github.com/leeleeian)

src/yb/tools/ts-cli.cc

@@ -469,6 +469,9 @@ Status TsAdminClient::FlushTablets(const std::string& tablet_id, bool is_compact
     return STATUS(IOError, "Failed to flush tablet: ",
                            resp.error().ShortDebugString());
   }
+  std::cout << "Successfully " << (is_compaction ? "compacted " : "flushed ")
+            << (tablet_id.empty() ? "all tablets" : "tablet <" + tablet_id + ">")
+            << std::endl;
   return Status::OK();
 }