`dump_tsm_test` has rare failures on testing for specific keys

In the inspect command `dump_tsm`, one of the tests `Test_DumpTSM_FilterKey` rarely fails in CI, as it sometimes does not have the String keys printed out from the command, despite showing that it has 3 keys present.

Error log from CircleCI:
```
"Summary:\n File: /mnt/ramdisk/dumptsm1787667073/2724524698.tsm\n Time Range: 1970-01-01T00:00:00Z - 1970-01-01T00:00:00Z\n Duration: 0s Series: 3 File Size: 226\n\nIndex:\n\n Pos\tMin Time\t\tMax Time\t\tOfs\tSize\tKey\tField\n 1\t1970-01-01T00:00:00Z\t1970-01-01T00:00:00Z\t5\t34\tcpu\t\nBlocks:\n Blk\tChk\t\tOfs\tLen\tType\tMin Time\t\tPoints\tEnc [T/V]\tLen [T/V]\n 0\t3824414228\t5\t30\tfloat64\t1970-01-01T00:00:00Z\t1\ts8b/gor\t\t9/19\n\nStatistics\n Blocks:\n Total: 3 Size: 102 Min: 30 Max: 30 Avg: 34\n Index:\n Total: 3 Size: 111\n Points:\n Total: 1\n Encoding:\n Timestamp: \tnone: 0 (0%) \ts8b: 1 (33%) \n Float: \tnone: 0 (0%) \tgor: 1 (33%) \n Compression:\n Per block: 102.00 bytes/point\n Total: 226.00 bytes/point\n" does not contain "foobar"
```