DEV: remove travis 32 bit job since it is running on azure

[mattip]

We now have an Azure job to test linux 32 bit, let's remove the job it replaces from travis

[charris]

@tylerjereddy Should we recommend docker rather than chroot for these types of tests?

[tylerjereddy]

As far as I can tell both approaches (Docker and chroot) share the host kernel. It seems that Docker is likely providing somewhat better "isolation" from the host, so maybe reducing the likelihood of accidental 64-bit things polluting the build is a good justification for using Docker.

One suggestion for making the clean-up in this PR more comprehensive -- tools/travis-test.sh contains a bunch of code & comments for 32-bit chroot build. There's an entire setup_chroot() function that I suppose can likely be deleted now, and probably the logic that handles dispatch to that function as well.

[mattip]

removed chroot from travis-test.sh

[tylerjereddy]

LGTM -- removes 60 lines of extraneous code / comments & I checked that Travis matrix is down to 11 entries from 12 on master.

[charris]

Docker looks more portable and easier to maintain, so lets go with that for now. Thanks Matti.

[charris]

Might be worth moving a few more things to azure. Travis gives us 5 parallel slots, so if we get down to <= 10 jobs we might save a couple or 5 minutes.

[charris]

There are also some tests that that look like they could be consolidated.