clean up tsdb for golint

[linearb]

An attempt to clean up tsdb for golint for issue #4098.

Not including meta.pg.go since that's generated.

Not sure about the following golint complaints, so left those unchanged:

$ golint tsdb/... | grep -v meta.pb.go
tsdb/functions.go:189:4: can probably use "var a []*rawQueryMapOutput" instead
tsdb/functions.go:229:4: can probably use "var val []float64" instead
tsdb/functions.go:235:4: can probably use "var a []float64" instead
tsdb/engine/tsm1/tsm1.go:85:2: don't use ALL_CAPS in Go names; use CamelCase

(Although did change some apparently unnecessary instances of make() into var.)

[otoolep]

Thanks @linearb -- we are actually doing some significant refactor in this code right now, so will hold off on merging this for now.

[linearb]

Sure thing.

[otoolep]

@linearb -- our major refactor of this code is complete. Can you rebase? It may be tricky, so you may like to re-do from start.

[linearb]

Yes, I can do it.

[linearb]

Hmm. Tests not passing consistently.

[linearb]

Tests pass now. Not sure why they failed after rebasing yesterday as the only thing
changed today was the commit message. CircleCI problem?

(Also, on some runs ran out of file descriptors locally for TestEngine_WriteCompaction_Concurrent
but raised limit and haven't seen errors since.)

Most of these changes are trivial.

But I made some changes from make() to var (which should be checked),
and left others alone:

golint ./... | fgrep -v meta.pb.go
functions.go:190:4: can probably use "var a []*rawQueryMapOutput" instead
functions.go:230:4: can probably use "var val []float64" instead
functions.go:236:4: can probably use "var a []float64" instead
engine/tsm1/tsm1.go:89:2: don't use ALL_CAPS in Go names; use CamelCase

[otoolep]

This is great @linearb -- I would like to merge. However the files underneath tsdb/engine/tsm1 are undergoing refactor at the moment. If you could just revert changes those files I will then merge.

Then we can revisit the tsm1 files. I am keen to merge this, I just don't want to stomp on that part of the tree.

[jwilder]

@linearb Can you rebase? #5196 removed a lot of this code and #5375 did similar changes.

[linearb]

ok - I'll have a look.

[toddboom]

Closing this out since a simple rebase is probably no longer feasible.