report status in .travis.yml correctly

[dhalbert]

Doing some command ; echo $? > status hid non-zero status from travis. Save the status and then use exit to simulate the command failure.

First push has a deliberate error to test this.

[dhalbert]

This does seem to fix "breaking the break the build" checking. There are errors in the first subjob from mp_map_t issues; I didn't attempt to fix those. The other subjobs are ok.

I originally tried:

  - some_long_command ; S=$? ; echo $S > status ; exit $S

but that causes the job to exit immediately due to the exit. You have to run the exit as as subshell:

  - some_long_command ; S=$? ; echo $S > status ; (exit $S)

[dhalbert]

@tannewt Or you could just cherry-pick this into your PR.

[tannewt]

I'm ok breaking the current build. Thanks!