(travis) Better diagnostics on *why* a build failed, reduce parellelism

This commit resulted in https://github.com/travis-ci/travis-ci/issues/2904

To mitigate run everything under 10 (not 32, not even 16) threads, hope
things will be allright. Although the real fix would be to 1) get the above
mentioned issue on travis fixed and 2) tuning the rdbms daemons to eat less
memory (both of these options are problematic).

The diags are *indispensable* when travis wakes up the OOMKiller
As a bonus add getstatus to all subshells for even better idea wtf just went
wrong