bogus test flags in usage output of some of our executables

[Dieterbe]

when #858 is merged, we have this problem:

github.com/grafana/metrictank/api imports github.com/prometheus/prometheus/promql, and see
prometheus/prometheus#3915

furthermore, metrictank, mt-store-cat, and mt-whisper-importer-reader import github.com/grafana/metrictank/api so those programs get all the irrelevant test flags.
which results in convoluted help/usage output.
not only that, but since some of the output is based on number of processors, we needed 950c786 to keep the CI scripts from failing.

[Dieterbe]

we should now be able to clean this up.
prometheus/prometheus#4400

[Dieterbe]

updating the prometheus code is non-trivial:

make
make all
make[1]: Entering directory '/home/dieter/go/src/github.com/grafana/metrictank'
make bin
make[2]: Entering directory '/home/dieter/go/src/github.com/grafana/metrictank'
./scripts/build.sh
+ go build -ldflags '-X main.gitHash=0.9.0-267-g9c5f84c' -o /home/dieter/go/src/github.com/grafana/metrictank/build/metrictank
# github.com/grafana/metrictank/api
../../api/api.go:74:38: not enough arguments in call to promql.NewEngine
	have (*Server, nil)
	want ("github.com/grafana/metrictank/vendor/github.com/go-kit/kit/log".Logger, prometheus.Registerer, int, time.Duration)
../../api/prometheus.go:138:45: not enough arguments in call to s.PromQueryEngine.NewRangeQuery
	have (string, time.Time, time.Time, time.Duration)
	want (storage.Queryable, string, time.Time, time.Time, time.Duration)
../../api/prometheus.go:182:47: not enough arguments in call to s.PromQueryEngine.NewInstantQuery
	have (string, time.Time)
	want (storage.Queryable, string, time.Time)
../../api/prometheus.go:246:21: not enough arguments in call to q.Select
	have ([]*labels.Matcher...)
	want (*storage.SelectParams, ...*labels.Matcher)
../../api/prometheus_querier.go:44:3: cannot use querier literal (type *querier) as type storage.Querier in return argument:
	*querier does not implement storage.Querier (wrong type for Select method)
		have Select(...*labels.Matcher) (storage.SeriesSet, error)
		want Select(*storage.SelectParams, ...*labels.Matcher) (storage.SeriesSet, error)
+ fail
+ echo 'Aborting due to failure.'
Aborting due to failure.
+ exit 2
make[2]: *** [Makefile:9: bin] Error 2
make[2]: Leaving directory '/home/dieter/go/src/github.com/grafana/metrictank'
make[1]: *** [Makefile:15: all] Error 2
make[1]: Leaving directory '/home/dieter/go/src/github.com/grafana/metrictank'
make: *** [Makefile:3: default] Error 2

and all of our prometheus people have more important stuff going on than this.