CI: travis: fix du -> df and capture it also directly from test

[jnpkrn]

No description provided.

[chrissie-c]

What's the reasoning behind the "#if 1" in check_ipc.c?

[jnpkrn]

It's conditionalizing part that perhaps someone will want to disable (e.g. downstream), for instance because the build/development environment also coincidentally exports CI environment variable and any byproduct is undesirable. Once we isolate and fix the original #234 issue, the whole bigger block should be dropped, but this is an extra convenience toggle for others to use.

[chrissie-c]

If you want to make it 'semi-conditional' then can you please make a #define for it and check for that. #if 1 is just unhelpful.

[jnpkrn]

OK, I have a better solution, but that requires #241 already merged as it also touches .travis.yml and would generate a merge conflict needlessly for that.

[jnpkrn]

I piggybacked also unification of custom.py tito extension with what's currently in pacemaker (for ease of maintenance).