The tsdb/tsm1 package was one of the test suites that took the longest
to run in platform with go test -short. The rule of thumb on the Go
project is that short mode should skip any individual test that takes
longer than one second. This change skips two such tests, and it
eliminates a string concatenation loop in two other tests, so that they
report completion in "0.00s" rather than about 0.94s, on my machine.
These cumulative changes take `go test -short ./tsdb/tsm1` from about 14
seconds to about 7 seconds on my machine.
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